I'm trying to use homebrew monsters in the maps VTT. When I first creature a homebrew monster, tit appears correctly in the VTT. When I make an edit to the monster, the changes to not show up. It doesn't matter if I delete the monster and re-add, or close the VTT and re-open.

DDB has separate services for things such as character sheets, homebrew, and yes, maps. Data has to be moved between these services, to save on bandwidth and improve load times it makes use of caching. The downside of this is that cached data can persist in one services even when it's source has been updated. This is most noticiable with homebrew where a change to a piece of homebrew can take a while to propagate. You'll most likely have to just wait until the maps service updates its cached data

So is there a way to force a cache refresh? If not there should be.

At the moment, unfortunately it just seems to be wait a bit

You seem to know more about computing, cache data etc than me, so forgive the question if it seems like you've already answered it above, I just want to double check my understanding.

I've created some home-brew creatures, changed their stat blocks and details on DDB.

When i view the details pages, it looks as if everything I've done has worked, and the text side of it reads perfectly as If it were lifted straight out of the MM. However, when I try to populate them into my DDB VTT, the stat blocks are still those of the "based on..." creature I used to build/nerf mine.

So is what you're saying simply that my creations WILL update and be usable in time as any other pre-populated creature, and I just need to allow DDB chance to update?

Thanks in advance for the clarity