Two apple computers, same problems. The desktop has one LR catalog only and the filmstrip will not allow the height to be adjusted by grabbing the top or bottom edge. The double arrow does not show up. Just above that is a information strip (part of the filmstrip) and it seems to be missing. The usual "1 selected of 800 images" message has been missing for about three weeks.
The second computer, a apple laptop has three LR catalogs and only one of the three has the problems mentioned above?
I uninstalled the LR on the desktop and without any solution.
I am not familiar with forums, so please forgive my learning curve/
Moved from Cloud forum.
This is a known problem with the last couple of releases of LR. See here for a workaround: Lightroom: Filmstrip is covering / overlapping filter- and breadcrumb bar | Photoshop Family Customer Community . Please add your me-too vote and the output from Help > System Info to that bug report, which will make it a little more likely Adobe will prioritize a fix.