Guys, I've posted the post below to the same but unmodded thread. I guess it is more appropriate to post it here. What I found: In the save file, I had this section: SCENARIO { name = ResourceScenario scene = 5, 7, 6 RESOURCE_SETTINGS { GameSeed = 1883583565 MaxDeltaTime = 21600 PLANET_SCAN_DATA { PlanetId = 1 } PLANET_SCAN_DATA { PlanetId = 2 } } } When I deleted both PLANET_SCAN_DATA with its bracketed contents (PlanetId = n), it worked. No more disapperaring part picker menu. It was a modded sandbox game. Mods: MechJeb, KerbalEngineer, USI Life Support, Kerbal inventory System, Exploration Pack, Karbonite, KarbonitePlus, MKS, Freight Transport, Exploration Pack. Probably not all mods needed. So it seems to me like when reverting to VAB something takes longer than it is supposed to (probably somehow connected with resources), and the part picker menu rendering just gives up. I really don't know. Spent a few hours editting save files, I guess I'm stuck in dead end. Steps to reproduce: - sandbox, other mods not tested - mods needed (listed above, probably not all needed) - fresh KSP install, fresh persistent save file - add the PLANET_SCAN_DATA sections - launch a simple ship (probe core, tank, Reliant engine) - part picker not appearing some 50-80% of times when reverting to VAB. Can take some 5-10 reverts for the bug to show. You dont have to fly the ship - it is ok to click Launch in VAB, then wait for the ship to appear on the launch pad, then Esc and revert to VAB.