Clearing the cache

I'm having a lot of problems with a series of jobs failing 100% of the time. There have been all sorts of weird issues with npm install not working, and I'd like to try and clear any caches that the runner is keeping. It would be useful if there were a way, from within gitlab, to tell a runner to delete all its caches (or the caches for a certain project).

In the meantime, is there a way of clearing the caches or am I going to have to hunt through the source code?