as the issue happens at always the same moments in the movie I guess someting in the subtitle triggers this (maybe a specific character). If we can discover what it is, a workaround can be made in Kodi or we can filter out that character in de subtitle stream while transcoding.
second option is to fix the source code. If you can give pointers to where to look I might spend some time on it.
Source is available on GitHub if you want to jump in, but keep in mind that Kodi v19 will probably be out within a month and a bit, so you are fixing something that will soon be deprecated.
There are a couple of open PRs to address this on the xbmc Git, but they are pending approval. They should solve the issue, but 3D won’t be supported on Pi in the next version of Kodi unfortunately.
What is the reason 3D is not supported anymore on the RPi? I see Kodi 19.3 (OSMC) recognises it is a 3D movie, and for some movies it even asks if it should play them as 3D or not, but yeah, then whateven you select it just plays the movie in 2D, which is really really a shame.