QRandomGenerator not random on certain Windows installations

I currently use QTemporaryFile on to generate unique names (template length of 8 X). On some win 7 & 10 systems I get bonkers results:

LHILHILH.pdf
OtNOtNOt.pdf
ZLsZLsZL.pdf

As you can see the template repeats after three characters. Reading the source code at https://github.com/qt/qtbase/blob/4ba535616b8d3dfda7fbe162c6513f3008c1077a/src/corelib/io/qtemporaryfile.cpp#L168 it becomes clear that one call to QRandomGenerator::generate serves as randomness for 3 characters. This is fine; but the issue I am seeing here is that subsequent calls generate the same random number. This happens only for on customer and I do not even know where to start debugging this...