You can disassemble, remove the guts (spring), tape it shut, and stuff it all in the connector bag before it starts messing with you. But if it's already giving you fits, that likely won't work. Also taping it and stuffing it only works short term as once water starts to collect inside it will lower the resistance enough to render that short term fix problematic also.
It won't help you on tomorrow's ride but this thread will help you avoid the issue entirely. It is about the TSS Bypass Jumpers I build to eliminate the TSS switch entirely. Giving you the freedom to run any throttle block, just remember to please always use a tether.
Thanks for the reply, we ended up just switching the whole throttle block for a different one. Will try and talk him into buying one of your Jumpers to keep in the tool kit just incase it happens again!