Cheers, masking worked. I don't use TTL anyway so its no real loss. Ive had the issue on a previous (550D) housing and the same on this. It also sometimes "crashes" and buttons stop responding and i need to power cycle the primary strobe to get control back.
I may just bypass it completely as above to prevent the problem coming back.
The controller has never been flooded but the housing does get varying amounts of condensation in and this does seem to affect it sometimes when it runs there. No real way around that as im in the tropics, high humidity and no aircon available.