We have:
1) 3 Mikrotik devices - hap AC2 (CAPSMAN)+cAP AC and Hex 750G r2 on other side.
2) L2TP+IPSEC tunnel
3) EOIP tunnel through VPN
4) EOIP interface Bridged to Virtual AP "Devices" interfaces defined in CAPsMAN configuration/datapath.

So the main idea is to L2 bridge some WiFi devices in office 1 to LAN bridge in office2 and make them available for discovery (mDNS).

When we set up EOIP tunnel, all looks fine. But when any of devices connects to "Devices" AP and get its address via DHCP (remote LAN), hap AC2 (CAPSMAN) just reboots. It would reboot every time any device connects to the AP. I tried stable and bug fix RouterOS versions - all the same except it worked for some time (day or two) on "bug fix" version but from some point it started to reboot again. Any suggestions? Do I need to provide full/partial configs for both devices? Could it be a hardware (temperature) problem?

check power supply

check power supply

You mean we should try to replace the power supply?

Workaround solution - use PPTP instead of L2TP+IPSEC. Also I'm going to try OVPN as L3.

Hey. Looks like a bug. Try long-term version.

P.S.: why don't you use just EoIP ver IPSec without L2TP?