I hope you don't mind me joining in--I don't meant to hijack the thread--but I am having a very similar problem with my Metal 52ac.
The setup I am aiming for is as a wifi ap-bridge to the wired network (ultimately this will be used in a closed network with no wan access). No NAT, no DHCP client (although it will become a DHCP server later on).
I think I have all the settings correct, but when I enable the bridge (with eth0 and wlan0 ports) then the wifi-lan bridging starts to work successfully, but at the same time I loose all access to WebFig (I'm on a Mac, so no Winbox). I have found that an existing ssh session stays live so I can now at least disable the bridge rather than reset and start all over (which I have done too many times now!).
Here is the current config, with the bridge disabled. Any help gratefully received.
# jan/21/2019 14:48:21 by RouterOS 6.43.8
# software id = 1K4A-AQNN
#
# model = Metal G-52SHPacn
# serial number = A80809E0DBD5
/interface bridge
add disabled=yes fast-forward=no name=bridge1
/interface ethernet
set [ find default-name=ether1 ] speed=100Mbps
/interface list
add comment=defconf name=WAN
add comment=defconf name=LAN
/interface wireless security-profiles
set [ find default=yes ] supplicant-identity=MikroTik
add authentication-types=wpa2-psk management-protection=allowed mode=\
dynamic-keys name=blue_planet supplicant-identity=MikroTik
/interface wireless
set [ find default-name=wlan1 ] band=5ghz-a/n/ac channel-width=\
20/40/80mhz-Ceee disabled=no frequency=auto mode=ap-bridge \
security-profile=blue_planet ssid="Video World"
/ip hotspot profile
set [ find default=yes ] html-directory=flash/hotspot
/ip pool
add name=default-dhcp ranges=192.168.1.101-192.168.1.254
/ip dhcp-server
add address-pool=default-dhcp disabled=no interface=wlan1 name=defconf
add address-pool=default-dhcp interface=wlan1 name=server1
/interface bridge port
add bridge=bridge1 interface=LAN
/ip neighbor discovery-settings
set discover-interface-list=LAN
/interface list member
add comment=defconf interface=ether1 list=LAN
add interface=wlan1 list=LAN
/ip address
add address=192.168.1.3/24 comment=sph interface=ether1 network=192.168.1.0
/ip dhcp-server network
add address=192.168.1.0/24 comment=defconf gateway=192.168.1.1
/ip dns
set allow-remote-requests=yes servers=192.168.1.1
/ip dns static
add address=192.168.88.1 name=router.lan
/ip firewall filter
add action=accept chain=input comment=\
"defconf: accept established,related,untracked" connection-state=\
established,related,untracked
add action=drop chain=input comment="defconf: drop invalid" connection-state=\
invalid
add action=accept chain=input comment="defconf: accept ICMP" protocol=icmp
add action=drop chain=input comment="defconf: drop all not coming from LAN" \
in-interface-list=!LAN
add action=accept chain=forward comment="defconf: accept in ipsec policy" \
ipsec-policy=in,ipsec
add action=accept chain=forward comment="defconf: accept out ipsec policy" \
ipsec-policy=out,ipsec
add action=fasttrack-connection chain=forward comment="defconf: fasttrack" \
connection-state=established,related
add action=accept chain=forward comment=\
"defconf: accept established,related, untracked" connection-state=\
established,related,untracked
add action=drop chain=forward comment="defconf: drop invalid" \
connection-state=invalid
add action=drop chain=forward comment=\
"defconf: drop all from WAN not DSTNATed" connection-nat-state=!dstnat \
connection-state=new in-interface-list=WAN
/ip route
add distance=1 gateway=192.168.1.1
/system clock
set time-zone-name=Europe/London
/syste
m ntp client
set enabled=yes
/tool mac-server
set allowed-interface-list=LAN
/tool mac-server mac-winbox
set allowed-interface-list=LAN