Mapping: Sun Temple has no exit to 2nd floor

Bug reference number: 1,032,672,497

I did Sun Temple layout with a T15 6-mod waystone. The first floor contained some abysses and also the Vaal Beacon for the current league. At the point where the exit to the 2nd floor should have been there is no portal to enter, not even an invisible one. Map is lost, can't progress to the boss.

This is a screenshot for reference: