Version 22.214.171.124 vorks fine with normal Microsoft .ppt files. Version 126.96.36.199 deletes some upper parts of slide headings, or do not show them. Loaded back version 188.8.131.52. and now situation is peaceful and OK. I do not need any answer. The problem lies in some program code.
Please file a bug report for that. Writing this here is simply useless, because this isn’t a place where developers look for bugs to fix.
Don’t forget to attach a reproducer document to your bug report, because being able to reproduce is essential to be able to fix.