Forgot to mention. Sorry.
To be correct: it doesn’t pop to zero, it only looks like that. Actually the value remains 0.0001 - as you can see when you increase the Edit-box-precision in the Bongo’s Options dialog:
Precision doesn’t go beyond 0.000001 (1e-6) though - the uppermost negative scaling Rhino itself allows. Also scaling up is best limited to 1e6 (1,000,000) to obtain acceptable accuracy. It all has to do with exactitudes in calculations with floating point numbers (the IEEE 754 doubles - Double-precision floating-point format - Wikipedia) used by the software. But that’s beyond my field of competence. 