Hi Justenuf,
When any problem is not repeatitive with same steps/ same environment, and occurs at random like in yoru case, it becomes difficult to find cause and fix.
Have you implemented Seamless Tabbing, this is not directly connected to the problem, but I guess this could help.
Have you checked the problem modules on different browsers or with different testers as different sessions may reveal more information about it.
if you have a vidoe playbar, you must be using the Event Vidoe, rather try switching to MultiSlide Synchronize video and you can add it to a single slide if you like and then use the main project playbar to control the video as well.
Thanks,
Anjaneai