What app are you viewing the resulting EPUB in?
My client took photos of how the pics were showing on his Kindle. Another friend of his also checked the epub on her Kindle and had the same result. I have an old Kindle and only one picture has the problem. There are no image problems when I view the epub in Adobe Digital editions on my PC.
So if the images are having problems on Kindles, then I need to solve it.
How are you preparing the EPUB to be MOBI on Kindle? What version of the Kindle app are your clients using and on what platform? Did you know that no two EPUB viewers ever seem to agree? Adobe Digital Editions is not a great previewer for EPUBs, nor MOBI on Kindle.
The client receives my epub file and converts it to mobi on his Apple computer. I am not sure with what software.
I use Calibre to convert my epub and load it to my old Kindle.
I have done around 10 books for my client with a similar styling and layout. Those books also had images in them and not so many. Those other books did not have this problem.
Has something changed recently with the export of images from InDesign to epub? Using the reflowable option?
I am not getting a solution here, which is worrying. My client will not be happy about the images not showing properly in the mobi file.
It is highly possible that your customer uses Kindlegen to convert the epub into mobi. Amazon made some changes during the last few updates of his software on how images are converted. Maybe you search in the forums from Amazon for a solution but don't expect to much.
You need also to know that there have been a few code changes for ePub with the last InDesign-Updates. ID is permanently evaluating, but this also means that the results must not always be stable or the same. If you really like to produce everytime the same code, you need to stick on the same InDesign-Version or you need to code you ePubs manually. This isn't very nice and can be frustrating, I know. But actually, this is the way it works.
That the 10 books before worked well sounds as to me as if you had good luck.
I found the solution to this one myself.
You need to set the images in the epub to export as png. The problem then disappears.
I found this as a hint on a forum elsewhere after doing a lot of searches. I can't find the forum link at the moment, but if I do I will post it here as well.
Problem solved and client is happy.