Setting a german locale [de_DE] (or other locales, using comma as decimal mark) leads to wrong outputs at least for x-axis acceleration (reading of -inf) and "nan" for pitch, roll and yaw.
It is only possible to get it working again by deleting the RTIMULib.ini file from the home directory (~/.config/sense_hat/) and setting a locale with "." as decimal mark to get a working copy of the file.
The values inside the RTIMULib.ini-file are correctly changed from "." to "," when the german locale is set, however the values seem wrong (only whole numbers and ,00000 as calibration values) and as written above, some readings are not working anymore at all.
Anyone having an idea where to fix this?