Random phrases and formatting being deleted on save within Rich Text editor

As the topic title states, according to our client sometimes phrases of text or individual formatting is reverted or deleted in the field after saving a content item. Most recently, two (but not all) of the bullets in a bulleted list were unformatted, and a piece of bold text was removed entirely.

This has happened intermittently for them in the past and they're beginning to be concerned about finding a firm solution or reasoning behind it. Since this is happening on the editor side, we don't believe it should be related to our front-end implementation and intake of the data. Have other users experienced this? Is there a cause that can be identified from these symptoms?

Hi David,

I'll be happy to help, but I'll need more information such as screenshots/recordings and the repo URL in question.