OpenWRT is a good-idea firmware running on consumer-grade hardware which almost definitely can't deal with what you're throwing at it.

Just beacuse you paid a bunch of money for it and flashed it with a better firmware doesn't make it good hardware, and custom firmwares often have poor support (and, on more than a few occasions, worse performance) than the default firmwares optimized by the manufacturer for the specific hardware they have.

The fact that you have to keep buying new hardware tells me that you have lousy hardware and should step up to proper hardware rather than expensive consumer-grade stuff.

Yes. Or you know, keep replacing the parts that break, the things with WiFi i them. These run stock firmware. The one with openwrt is now for routing and firewall only and works fine. (Wifi disabled, Ethernet only.) A benefit to replacing wifi gear so far has been to keep one step ahead of the neighbours in the wifi spectrum. Gets crowded signal wise downtown.