Quark: 4.0 - 438
Zeta: 1.0 - 14

In the latest build, I have noticed that various blocks are not connecting with the sides of vertical slabs. Have tested with the connection option disable in the config

are those Quark's vertical slabs?
I tested it and it works normally, so if those are from quark, some mod may be breaking the tags

After some testing, it appears that v1.1.10 of Amendments is the culprit.
Existing connections were fine but I was unable to create new connections with amendments installed. I will report this bug over at their github