In advance:
- Our external writers send us InDesign CC files (idml and indd)
- We open and save them in InDesign CS6
- Our customers use InDesign CS6

1. Version:
   InDesign CS6 8.0
   InDesign CC from 12.0 to 14.0.2 (others not tested)

2. Steps:
   Since when: between 10 and 17. April 2019 (last time it worked on 10. April 2019)

2.a Open InDesign CC (any version, i tested 12.0, 13.1, 14.0.1 and 14.0.2)
2.b Save a file with activated hypenation (either indd or idml, both tested)
2.c Open either one of 2.b. in CS6

1. Expected result:
   Hypenation works as usual in CS6. Text fits frames.

2. Actual result:

3. Hypenation doesn't work in CS6 which resluts in text frames having overflow

4. Test files and information:
   Already tested:

5. de- and reactivating hypenation in CS6

6. checking for "no break" option

7. checking every used paragraph- and character-format

8. checking user dictionary options

9. checking language options

10. checking autocorrection options

11. saved the file as idml and indd in CC 12.0, 13.1, 14.0.1, 14.0.2 and then opened it in CS6

12. contacted support