Unable to backtrack in already explored delves

I tried to backtrack through a formerly explored delve to check if i had explored all the caves between two waypoints and arrived at a point where i could not continue.
An unbroken wall that shouldn't be there stopped my progress.

https://imgur.com/a/T9HKHSs

ref no.: 252.131.511

Prety sure it should be there.

The delves are loaded in blocks, the bit you are at is the transition between 1 block and the other, when you ran the area the first time it would have resulted in a load screen.