Cursor Jumps to end of page when editing

While I am editing a page, the cursor will jump to the very end of the html code at the bottom. OR, I will get a white screen of death and lose anything I have typed in. This started about 2 months ago for 2 websites and for multiple people. I just had our IT guy review and fix a few issues with old PHP and a missing file from the theme. But these changes did not fix the issues. It does seem like I can type more letters than before.

I see no issues with the actual live website. It’s only when editing a portfolio item.

You can see the situation at 32 seconds into the video at:

The white screen of death is at 10 seconds in this video:

https://media.transformanceadvisors.com/multiple/20231229163225.mp4

I’ve searched the topic and find similar, but always different situations.

10 plug-ins are all current. WordPress is at 6.4.2

The theme is old and maybe something is new with WordPress which is not compatible?

The page I need help with: [log in to see the link]