Acrobat Pro / Reader DC: Cannot copy-paste German umlauts into comments

Hi everyone, I've got a rather strange but extremly troubling problem:

In Acrobat (Pro or Reader) DC, when copying and pasting a word containing the German umlaut characters Ä,Ö,Ü,ä,ö,ü or an ß the characters will be transformed into A,O,U,a,o,u and s upon pasting them if certain other characters are present that use the same font face. We have seen this problem across different OSes, in Acrobat Pro DC as well as Acrobat Reader DC. This issue is causing us extreme trouble, since we are handling thousands of hundreds pages long documents where we need to use the PDF commenting tools for adding corrections.

Does anyone here have the same problem and / or a solution? Thanks a lot!

System:
OS: Windows 10 Enterprise 20H2, Build 19042.1526
OS-Language: German
InDesign / Acrobat Application Language: German

Steps to reproduce:

1. Start InDesign 17.1 x64 (currently in use, error was reproducible with previous versions back to 15)
2. Open a default New Document
3. Add a text frame
4. Add any or all of the following common German words

Änderung
Öfen
Überblick

Käse
Kröte
Blüte

Maß
groß
Gruß

mäßigen
größer
grüßen

AND add one or all of these characters:

≥ (Greater-than-or-equal-to-sign)
⁰ (Superscript zero)
σ (Greek small letter Sigma)
⅞ (Vulgar fraction seven eights)

(This list is by far from exhaustive, I've observed many more "problematic" characters...)

5. Export PDF with any of the PDF-Presets PDF/X-4:2010, PDF/X-3:2002, PDF/X-3:2001, PDF/X-1a:2001 , PDF/X-1a:2002 (again, this is not exhaustive by any means, but I've stuck to the presets for conformance and reproducibility)

6. Open the exported PDF in Adobe Acrobat Pro DC (currently in use: 2021.011.20039) oder Adobe Acrobat Reader (currently in use: 2021.011.20039)
7. Open the PDF commenting tools
8. Double Click one of the words to select it
9. Press Ctrl + C (PC) or Cmd + C (Mac) to copy
10. Press Ctrl + V (PC) or Cmd + V (Mac) to paste

Result: Ä,Ö,Ü,ä,ö,ü and ß will not paste correctly

Suspected cause:
Acrobat is unable to handle the simultaneous existence of Ä,Ö,Ü,ä,ö,ü, ß and ≥ OR ⁰ OR σ OR ⅞ (or many others) within the same font face when pasting text.

Indication that it's not related to third party fonts:
The testing was done with Minion Pro default font.

Indication that it's related to font face:
Go back to InDesign, change font face for the ≥ / ⁰ / σ / ⅞ to Minion Pro Bold and repeat steps 5 to 9. The Ä,Ö,Ü,ä,ö,ü and ß will now paste correctly. If you change any of the words to Minion Pro Bold, the error will re-occur.

Indication that it's a pasting error specific to Adobe Acrobat Pro/Reader:
Pasting the word copied in step 8 works perfectly fine in other applications like MS Word, Google Chrome Browser, and even InDesign or Photoshop.