2011 Mazda3 remote
 

Both original remotes are now behaving irregularly. Each has new batteries, and sometimes they work and sometimes they don't This has been going on for several months now, and as far as I can recollect, both keys exhibited the intermittent symptoms at or nearly the same time. It has now gotten worse, be each still occasionally work.
Any ideas as what to check? Here's one of my remotes:

https://cimg5.ibsrv.net/gimg/www.maz...b4c0a6a67d.jpg