Would I be correct in assuming that you gave the WAN interface the name "VDSL" when you originally defined the interface?
What I'm trying to rationalise is that if you had named the interface "zyxxy" then you would have seen --
Feb 26 01:54:19 user.notice zcmd: System: Wan interface zyxxy connection lost
Feb 26 03:38:15 user.notice zcmd: System: Wan interface zyxxy connection ready
We really need to see the context of, say three lines, around both of those two messages.
What cold cause loss of VDSL on WAN for that long without dropping the sync.
Am I interpreting your query correctly? That the WAN interface connection was reported "lost" at 01:54:19 and was reported "ready" 03:38:15 with nothing else logged in between those two messages?
Perhaps a problem with the device's system logging process?