I'm having the same problem on the latest long-term version. Updated to the latest stable 6.48.1 and the problem is still there. Disabled all firewall rules, rebooted the thing, nothing woks. If I remove the mikrotik and connect directly, it's all good. Haven't had this something like this happen before.
# feb/10/2021 13:54:23 by RouterOS 6.48.1
# software id = ALVT-L4PT
#
# model = 951G-2HnD
# serial number = 642E051364F4
/interface bridge
add fast-forward=no name=Conferinta
add fast-forward=no name=Guest
add fast-forward=no name=Privat
/interface ethernet
set [ find default-name=ether1 ] name="ether1 - Orange"
set [ find default-name=ether2 ]
set [ find default-name=ether3 ]
set [ find default-name=ether4 ]
set [ find default-name=ether5 ] name=ether5-RDS
/ip pool
add name=dhcp_pool1 ranges=192.168.11.2-192.168.11.254
add name=guest ranges=172.16.22.100-172.16.22.250
add name=conferinta ranges=172.16.33.100-172.16.33.250
/ip dhcp-server
add address-pool=dhcp_pool1 authoritative=after-2sec-delay disabled=no \
interface=Privat name=dhcp1
add address-pool=guest authoritative=after-2sec-delay disabled=no interface=\
Guest name=server1
add address-pool=conferinta authoritative=after-2sec-delay disabled=no \
interface=Conferinta name=server2
/interface bridge port
add bridge=Guest hw=no interface=ether3
add bridge=Conferinta hw=no interface=ether4
add bridge=Guest interface=wlan1
add bridge=Privat hw=no interface=ether2
/ip neighbor discovery-settings
set discover-interface-list=!dynamic
/ip address
add address=192.168.11.1/24 interface=Privat network=192.168.11.0
add address=172.16.22.1/24 interface=Guest network=172.16.22.0
add address=172.16.33.1/24 interface=Conferinta network=172.16.33.0
add address=82.XX/16 interface=ether5-RDS network=82.XX.0.0
/ip cloud
set ddns-enabled=yes
/ip dhcp-server network
add address=172.16.22.0/24 dns-server=213.154.124.1,8.8.8.8 gateway=\
172.16.22.1
add address=172.16.33.0/24 dns-server=213.154.124.1,8.8.8.8 gateway=\
172.16.33.1
add address=192.168.11.0/24 dns-server=213.154.124.1,8.8.8.8 gateway=\
192.168.11.1
/ip dns
set servers=1.1.1.1,9.9.9.9
/ip firewall nat
add action=masquerade chain=srcnat out-interface=ether5-RDS
add action=masquerade chain=srcnat out-interface="ether1 - Orange"
/ip route
add check-gateway=ping distance=1 gateway=82.XX
add check-gateway=ping distance=2 gateway=192.168.1.1
add distance=1 dst-address=8.8.4.4/32 gateway=82.XX
add disabled=yes distance=1 dst-address=192.168.11.0/24 gateway=10.20.30.2
set api-ssl disabled=yes
/ip ssh
set allow-none-crypto=yes forwarding-enabled=remote
/system clock
set time-zone-name=Europe/Bucharest
/system logging
set 0 topics=info,!dhcp
\n/tool netwatch disable numbers=1"