Joy Con wireless signal is unreliable, but Pro Controller is fine

I have an issue with my Switch where whenever I play with my Joy Cons wirelessly, the signal regularly drops out for a few seconds. Button presses don’t register, motions don’t work, stick directions get stuck briefly, etc. It’s definitely not Joy Con drift—I have dealt with that separately and fixed it myself. This problem happens with brand-new Joy Cons and even other people’s Joy Cons with my Switch. I don’t have issues when the Joy Cons are connected. Pro Controllers work perfectly, as well as my PowerA Wireless GameCube-style controller. Oddly, I have similar issues using the 8bitdo USB adapter with an Xbox One controller, but I don’t know if that’s related or just an issue with the adapter.

So, I’m pretty sure this is a problem with my Switch itself. I don’t think it’s my Bluetooth antenna since other controller types work fine. I suspect there is some other hardware that’s not processing wireless Joy Con signals correctly, but I don’t know what that would be or how to go about repairing it. Is there any part of the console I could try to replace, or should I just start saving for a Switch Pro?