I'm including the save file, WIP mod and logfile from a crashing run. To reproduce, extend the underground pipes into the forest, then wait for a bit for modded pipes to generate.
The code for modded pipes is in `modules/oil.lua`.
Thanks for the report. Issue is now fixed for 2.0.46.
Issue was a fault in the logic which selects a sprite to draw when a "pipe" has multiple connections facing the same side.
Please note your mod is trying to use diagonal pipe connections which are illegal - some pieces of logic interpret them as being not diagonal and this is why your pipes are causing issues because the game thinks those are facing cardinal directions. For 2.0.46 i will remove ability of mods specifying diagonal directions for fluid box connections because they are just bad and they cause a lot of issues around the code, and those are simply not supported anyway.