I’ve been a premium member for years and I’m also very frustrated by this issue. I first started observing it, and reported it, about a year ago. I’ve tried a number of work-arounds, including:
Going back to a prior version of the note. This has not worked well. Once a note has an indent problem, it re-surfaces right away
Avoid accessing Evernote from a browser - this seems to solve the problem but also removes one of the biggest benefits that is supposed to be included in Evernote. And there are still certain functions I have trouble finding in the app.
.Finally, this is my work around:
.. adding dots at the beginning of the indented paragraphs so I can still function after the indent corruption occurs on that note.
... and more dots with each indentation. Hopefully my indentations in this post will remain intact so my message is clear.