Clearance exactly at the limits of the design rules

I’m finding that Pcbnew (BZR6086) won’t let me route tracks with clearances equal to the clearance setting in the design rules. I was able to do this in an older build. My settings are 0.1 mm track/space and I’m routing on an 0.05 mm grid. If I lay a trace as close as possible to one that is on grid, it’s about 10 nm off the grid. If I disable DRC and route on grid with exact 0.1 mm gaps, it fails DRC.

Any suggestions to work around or fix this? I’m using Eurocircuits and they don’t offer any finer rules on their pooled service. Setting the DRC clearance to 0.09995 mm clears the errors, but then I might route things too close and fail Eurocircuits DRC which is quite strict.

I’m trying to break out an 0.8 mm BGA with 0.5 mm via pads. That leaves exactly 0.3 mm between vias which should just fit a single 0.1 mm track.