I think that one of the factors (they are certainly many) leading to these premature draws is that the default victory conditions are set too low on this map, the WW4 map, and some others. The Imperial II variant was designed to have a victory condition of 84 centers, but when adapted for this site it was arbitrarily assigned a VC of 70 centers. This map has been played hundreds if not thousands of times over a decade and never was there any feedback suggesting that the victory conditions be lowered. The 70 SC level may only be 14 centers lower than the 84 necessary to wind with 50%+1, but it significantly changes the dynamics of the game. As Alcuin points out about the above linked game, a general panic went out around the board when Turkey got to 40 SCs, still 30 centers away from victory. Rather than play the game with diplomacy players began playing for stalemate lines, and demanding a 10 player (out of the original 13) draw. The game quickly deteriorated into finger pointing and off board rumor mongering, which distract several salient points about this variant. First of all as Alcuin again notes, all of the supposedly unstoppable colonial powers (Britian, France, and Holland) were destroyed, as were the next tier of regionally concentrated powers (Russia and China). It's been alleged that these powers are heavily advantaged at the start of the game, but this game demonstrated what strong play and strong alliances from other powers can accomplish. Japan and Brazil established very strong global positions from meager beginnings debunking the myth that the small nations are unreasonably disadvantaged.
Unfortunately the low victory condition platform drove the game in a direction that destroyed the game. On one hand it's great that no one wants to see a solo, but when you set a "solo" criterion below 50% of the total centers, it destroys the dynamics of the game, and you have people scrambling to set up stalemate lines in the mid game rather than the end game. The bottom line is that this variant needs to be reset with the default victory conditions at 84 supply centers.
Of course that's only the start of the fix to the issue with the premature race to draw games here, and we have not even touched on the fact that the PPSC model encourages players to accept/allow solos because they score more VDip points by losing than they would in playing to force a draw. The two facots collide when your option is to vote for a 10 player draw and gain very few points, or to tolerate a solo and rake in lots of points. The system is broken here, and it's ruining the gaming experience.