seems only tx is affected on r3, as i see packets on the vlan from my laptopI don't have a setup to test 6.2 on my MT7986 board right now, but I did test latest OpenWrt with my changes and couldn't reproduce the issue there.
tcpdump on R3 (e4:b9:7a:f7:c4:8b is mac from laptop):
13:47:05.265508 e4:b9:7a:f7:c4:8b > ff:ff:ff:ff:ff:ff, ethertype 802.1Q (0x8100), length 577: vlan 500, p 0, ethertype IPv4 (0x0800), 192.168.50.2.59389 > 192.168.50.255.21027: UDP, length 531
13:47:05.265548 e4:b9:7a:f7:c4:8b > ff:ff:ff:ff:ff:ff, ethertype 802.1Q (0x8100), length 577: vlan 600, p 0, ethertype IPv4 (0x0800), 192.168.60.2.59389 > 192.168.60.255.21027: UDP, length 531
regards Frank