1.8, comma decimal separator, a diplomacy bug.
I have a quick and dirty test game where I have 3 player races to test trade mechanics, but I ran into a bug with diplomacy (in addition to the fact that currently, the races do not seem to trade with each other). We'll call them races A, B & C. Races A & B started on Sol, on different planets and I SM'd the communications, but the civilians refused to trade with the other race, possibly because there's not enough profit in the same system trade for them. So I figured I'd create another race couple jumps away with a stabilized highway from Sol to there. So race C is 3 jumps away, and I spawned in a race A diplo ship there to open up negotiations more naturally, in due time race A opened communications with C, but C was still attempting to communicate to A and A was now refusing since they already had communications established. So I made a C colony on Luna and spawned their diplo ship there to open communications with B and hopefully with A. Now C has communications with B, but they refuse to let B to establish the same. This might explain why some other players have had trouble communicating with NPRs: the NPR established communications and no longer needs to partake in doing it the other way around. Perhaps as a fix, once one side establishes communications the counterpart does it as well, no matter how far they are in the progress.
Edit: After 3 years and setting communications in SM, still no foreign trade what-so-ever. I even tried making A's colony on Venus a military colony to stop the traders, but the freighters going there simply stopped and a freighter they built on Earth did nothing. After I took the restriction away all freighters returned ferrying infra to Venus.