I can confirm that if you open a files as a smart object via ACR CC 2018 19.1.1 it does not get recorded in the open recent file list. If you open it as a background layer it will be recorded. Its a CC 2018 19..1 bug. Pleas report the bug at Photoshop Family Customer Community
I have not notice any actions being changer by CC 2018 however most of my actions do not have save steps. Do you know what triggers the bug. You did not state when the steps are changed.
ACR settings would be recorded in Your smart object layer RAW object or your Smart Object layer Smart ACR filter. If you use the ACR Filter on a pixels layer the layer would be altered and no ACR setting would be recorded. A snapshot is a snapshot of the document ACR settings would should not be removed in a snapshot. Are they missing in a RAW file Object or a ACR Smart Filter?
I posted to Photoshop Family Customer Community.
As far as actions- I have many actions, involving various steps, usually ending with several save option. In 3 different actions that I looked at, the same final save action, to save as a quality 9 jpg to a specific location had change to a different location entirely, on all 3 different actions. One action I could see maybe something went wrong and it had an issue, but why would all 3 change like that? The saved location still exists unchanged, so not sure why it was altered in the actions.
I am talking about snapshots in the ACR window- I always save the initial settings I have set, then after making subsequent changes to values, I save those setting as well so I can always go back to earlier ones as needed. So this occurs out of any steps take in Photoshop proper, such as filters or tools. I expect those snapshots to be saved in the internal database, so when I open that raw file next time I can go back to that snapshot(s) and one the file with those setting used. That is the way it works when I open a file not as a smart object, and when changing settings while open as a smart object, the ACR window lets me save my changes as a new snapshot, so why are those snapshot nots saved as they are other times? Thanks.
Action show not change unless you edit them. I have never seen any of my action change other the ones I edit. I do not believe you can record an that will modify itself or any other action. You may be able to create a script to modify an action. XTools has script the can create and XML file from and Atn file Which can be edited and the updated XML file can in turn be made into an atn file so a script could do it. If you see action are changing on your system you should try to fine our when they change. It is possible also to load an action set more than once and edit actions in one set and not the other and it also possible have an Actions with a Name X in more the one action sets where the action a similar but not the same. Make sure you not seeing different action with the same actions action name.
I have never used snapshots in ACR but I have lost ACR settings. That I did not realize right away I was and when I did loose them I did not know why. What was happening follows: I has set my ACR setting to save sidecar files with ACR settings not use ACR database. All was fine and I though all was working. However I was not quite right. I had Copied Some RAW files into C:\ when I did I has to provide the ACRAdministrators Permissions so I did. No big deal. When I edit the RAW files ACR setting were being saved and I would seem the the next time I opened the image RAW file in ACR. Everything was working. Not quite.... They were not being saved in sidecar files in C:\ and there were no error messaged generated. The ACR setting were also not being saved in ACR database. They were only being saved in ACR Cache.... "C:\Users\userid\AppData\Local\Adobe\CameraRaw\Cache" Caches purge stale data out and caches are sometime Purged.... Bye bye ACR settings. Snapshots should be save in Sidecar files or your ACR database.
I have in the past had case where I renamed a folder that was specified in an action, causing it to either ask for a new location, or default to a different location. Can't remember details off the top of my head. I have 3 similar actions, all clearly marked with the name of the action, but all saving final image to same folder. Also, if I accidentally change one action it would not affect other two, and folder where action now tries to save jpeg to is nowhere I would ever have selected, so it does not add up.
I just looked back at some versions of my actions I archived previously- reloaded them and looked closely- the same step was changed on those 3 action I saved on 1/22/18, even though I have used that set of action since then, which saved files to correct location. So basically, previously saved actions have had their file save location changed retroactively!
As far as ACR, I do have it set in Photoshop raw preferences to save changes to xmp files, which it seems to do automatically, although Lightroom prompts me to do so as well. Have never had an issue that I know of of settings not being saved. I guess I never thought of ACR snapshots being saved in xmp same as any other settings, instead in some sort of ACR database, but in xmp makes sense. Just not sure if this is a bug where saved snapshots are not being saved, or a...design feature.
I am on a Mac, OS 10.12.6.
I use windows and do not use lightroom. I have never seen any action change except for the action I edit and change. If you double click one an action step you would be editing that step. The Action Palette is a full function action editor as well as a recorder and player.