Access point TL-WA701ND VLAN MultiSSID MTU problem?

Question

network hardware

Good day.
I recently purchased an access point for a small office and ran into a problem in working with MultiSSID (organizing an additional guest point on another vlan). That is, everything is fine, but with this mode of operation there are problems with access to some sites (almost all). I found an article about the problem with Multi-SSID where it is described and realized that I need to update the firmware.
Someone has already updated this firmware (it's just not from the official site), how does the TL-WA701ND access point work and what are the bugs, if any ???