No rear brake again

My 2020 bike had recall for new large master 18 month ago, thought it was getting a bit spongy again towards the end of last summer,but after 4 month storage,no back brake again,thought that Triumph had finally fixed it with recall, but now back to bleeding myself again.

It makes me wonder if the ABS cylinder is leaking thru. It may not have any external leaks but if the piston has a leak path, you'll get spongy brakes.