Looks like the same issue as T6991, only it happens in VRF.

Steps to reproduce:

• Create interface with DHCP and assign to VRF
• Have no protocols static entry under VRF
• Observe DHCP default route exists in show ip route vrf ...
• Make a change to the VRF that regenerates FRR config, for example set vrf ... ipv6 disable-forwarding and commit
• Observe DHCP default route no longer exists in show ip route vrf ...