Yes, i’ve tried 3.0e-5 (1.5 times lower) compressibility for both membrane and water and got only one “Pressure scaling” warning in the very beginning (60000 step) of the simulation. If i keep one of the groups (memb or solv) compressibilities at 4.5e-5, system is less, but still instable. Lowering compressibilities to 1.5e-5 leads to no warnings at all, but i doubt about how physical these values are. Of course, simulations were carried out with nst(p/t)couple equal to 100.
Also, i’ve tried to calculate compressibility as given in How to determine compressibility? thread, but came up with numbers twice bigger than 4.5e-5 bar-1. System exploding almost instantaneously with that values being set.
Thank you for your suggestions and overall help.