You might try to use the Bolton settings to see if they work. Changes from your settings are in bold.
P1 = 100
P2 = 5
P3 = 1 - when this value is 0, throttle max power is determined by the PAS level. when it's 1, max throttle is allowed regardless of PAS level.
P4 = 0
P5 = 0 - This value is used to try and correct/smooth the battery % remaining. 0 just shows the real time voltage so it may drop when under load. You could leave this at 15.
C1 = 3
C2 =0
C3 =1 - this just determines the default assist level when you turn on the bike.
C4 = 0 - this allows max speed from the throttle even when you're not pedalling
C5 = 2 - this value limits the max current. Bolton recommends lowering it to about 30 amps because the motor cable connector can't handle 35 amps.
C6 =3
C7 = 1
C8 = 0
C9 = 0
C10 = N
C11 = 0
C12 = 4 - this determines the low voltage cutoff. 4 is the default value. lower values reduce the minimum voltage. higher values raise it.
C13 = 0
C14 = 1 - this is the strength of the pedal assist. It shouldn't affect the problem you're having. 1 is weak, 2 is medium and 3 is strong. I would leave yours at 2.
Let me know if that changes anything. The other possible issue is that the pinouts on the throttle and PAS on your bike are different from the Bolton controller. Higo connectors make changing the pinouts very difficult.