hello binoy,

first thing is to check the battery charge and make sure it is fully charged, check cells and make sure no bad cells and fluid level is up to correct level.

second thing is a model and serial number of machine would be helpful
third thing is when error occurs does display show an error code?

fourth thing is now i have to ask, what sort of modification did you do to current sensor? Any alteration to the current sensor will probably cause problems but generally would cause them in both directions, not just reverse. It does mount between the Neg and A2 connection on drive circuit on panel and the yellow and green wires run to terminals 3 and 4 on the "Z" plug on oscillator card. So what modification did you do?

fifth thing is have you checked the contact tips in fwd/rev contactor for burning and wear? check the armature and insulators in the contactor for wear and alignment? If you are not getting good connection on the tips that can cause a drop out and poor running conditions. Generally this is accompanied by some error code on display when fault occurs.

some of the codes you may witness on the display are -03, -15, -23, -24, -42, -43, -47 and so on. Do you see any codes on display when error occurs?