Fault code 500 Bosch active line plus

[Power to go]

Bought a Cannondale neo road bike second hand (18kgs) 2x 10 speed , and all going well. Lately is is giving the alarm code 500. If I set off on the bike, I feel the motor assisting, if I stop pedaling and start again, it does not come back on. If I come to a stop and start pedaling again it assists again. Sometimes if the code 500 comes up, it still assists. Living in Ireland, it worth repairing or getting a new motor unit.

 

[Power to go]

Opened motor, water had got in and end shield bearings are rough, the needle bearing and motor engagement was all seized as well. Freed out, reassembled as I wanted to see of it was working before getting bearings. All going well. Ordered bearings, fitted end shield only as the alu plastic cog needle bearing looked difficult to remove. Reassembled, now turning smooth in my hand, put back on and it is not working as normal. The motor seems to be cutting in for a couple of seconds when on the flat or about 2 seconds when on a incline, cuts in again shortly afterwards. Any ideas?