Arcing starter!! HELP

[Ac490]

Hi caddy owners

So my caddy 1.6 tdi has an intermittent fault with its starter can anyone shed some light on it? So sometimes when I go to start my van it won't start and you can hear a cracking sparking noise from the starter. Got my wife to turn the key one of the times it did this an I looked under the bonnet. There was blue sparks dancing off the starter. I have removed the starter and disassembled it cleaned everything rebuilt it. It then worked for a while. Then it's gone back to doing this now and again a few times since. A tap on the starter with a hammer and it starts . But it's annoying. And this time of year isn't nice laying on the wet ground to give it a tap to get it started . When I had starter off I used jump leads to test it and it spun up nice and kicked out the starter pinion fine. ? Oh I have also replaced the battery with a bigger beefier one and the starter is still the same can work for weeks if not months then suddenly for a few days arcing and won't start until you give it a tap So anyone have any ideas or have had this issue??

Thanks

[Doc]

Are the power terminals clean?
You might find if it's been arcing it will have eroded the terminals a bit and this can cause a bad connection.
The main power terminal is done up tight on it and not just bound up on some arc snots?

[Ac490]

Thanks for reply once I get some better weather I'll get the air box out again and I'll check everything over clean all connections and check it's all tight

Thanks