To Reproduce:

1. Open the the attached 'repro a17' zip, open & run 'ReproScene'.
2. Run observe the "count <= std::numeric_limits<UInt16>::max()" error.
3. It is thrown after ouputting relatively long strings >20 000 chars to the debug console.
4. Error is not thrown exactly after "Debug.Log" (or print), but only after some time has passed (not thrown if >20k strings are filtered out).
5. The string seems to be outputted successfully despite the error (not sure if it is fully outputted, though).

Might be related to 517825, but happens on much shorter strings, there is no freezing and can't be reproduced on 4.*.