mwlwifi is known to have interoperability issues with esp8266 since day 1, chances for this to get fixed are effectively zero - Marvell didn't care during their tenure, NXP's only action was EOL'ing the 802.11ac chipsets.
In this situation the third radio (sdio/ mwifiex) might actually be more cooperative, but this easily introduces regdom issues and this radio was more meant to be used on the 5 GHz (for passive continuous DFS scans, although Linksys never actually deployed this feature) and doesn't really come with proper antennas either.