Key fobs for two different 2012 Priuses intermittently work

My husband and I both own a 2012 Prius. Mine is a 4 and his is a 3 (I think I've got the trims right, it's been a long time since I've thought about it). We've owned them since 2014, they each had only one other owner and we have been diligent with keeping up with the scheduled maintenance at the dealership we bought them from.

He has always consistently had an intermittent problem with his key fobs for both of our cars. The car will say low battery, or it won't unlock at all, or it'll say no key detected when I get out and take my keys but he's still there with his, or it might only unlock when you use the button on the key fob. Later the same day it might work again, or it might not, only to work again later in the day.

There is absolutely no consistency to this issue, other than it's always just a problem with his fobs and it's with both cars. The same location, like our house, will work sometimes and not other times. It happens both when I'm with him and when he's alone, and only has his key fob with him.

He carries his keys, a wallet, and one or two cell phones (one with no service and always in airplane mode that is his eReader) in his pockets. He carries his wallet and phone(s) in one pocket and his keys in the other. He has a phone with nfc, but it's never used and this problem happened before he got this current phone. I also have a phone with nfc capabilities, never used that capability and I often carry my phone in my purse next to my keys. The only difference between our phones is I have an iPhone and he has a Google Pixel.

We are just baffled. We haven't tried swapping fobs and seeing if the problem persists. Please help!

 

Multiple times.