I noticed this recently, but not sure when exactly this started happening, possibly with the 0.42 update.

Any german Umlaute are affected by this, but I assume this might be a general UTF-8 encoding issue.

Here it is in the upload form before uploading:

Here is the document after uploading without modifying it:

I feels like a classic case of interpreting UTF-8 as ASCII/ISO 8859-1 on the byte level.