Hi there, I've recently noticed that the right rear indicator bulb doesn't always flash, making me think it's a bad earth somewhere. I've removed the bulb and put it back in a few times making sure it is actually working still, then replace the lens cover before riding off, only to discover that it's not working again when I get home after less than half an hour. I'm not ruling out some really rough sections of road which are on my route home from work, but don't think it's the primary cause. 

Just wondering if I should spray a little WD40 on the bulb contacts, and or replace the globe just in case? 

Cheers.

Easy fix, don't turn right.

NEVER spray WD40 on contacts. Wipe clean with Carby cleaner and that should do it. I would:
1. Replace the actual bulb
2. The earth is normally the stem and bolt holding the indicator to the bike so loosen and clean things there and re-tighten.
3. It could be a loose fitting or wire somewhere in the path up to the indicator so you may need to trace things back.

2 wire...damn they have changed since the 80's lol. I have a can of CRC Contact Cleaner too...darn good stuff.

In that case tracing the cables back through all the connectors and spraying them with Contact Cleaner would be my next option after replacing the bulb.