Negative current reporting at high erpm in no-load setup

I just set up a V 4.10 VESC and tested with a small 35mm motor, with no load attached. Running quite smooth.

But the higher the speed, the more negative the reported motor current (up to -1A @ 60'000 ERPM) and also batt current. Constant speed, so no regeneration situation.
For this idle testing, I use a power supply. It displays that 1..2A are going into the VESC, which is as expected.

Where does this negative current reporting come from?

Linked to this situation might be, that if I configure an ERPM limit, the motor speeds up even faster when crossing the limit, instead of staying at the configured max. ERPM.