[axn]

21317 has ECM done till half t45. If you convert that to a TF depth and use that instead of 67, maybe it will generate reasonable B2?

EDIT:- Or realize that asking P95 to generate "optimal" B2 with completely made up numbers like "67,2" is piling nonsense upon nonsense, and instead just specify the B2 manually (say B1*200).

EDIT2:- But naturally, this small an exponent should use GMP-ECM to do stage 2.