cst accurate simulation of a 435 MHz helix antenna

Hello,
I'm designing a 21 turns 435 MHz helix antenna (L=2 wavelength) and simulate with transient analysis: with 4,9 M mesh cells it takes around > 28 hours and 1K staircase cells. Maximum gain simulated is at 400 MHz VS 435 MHz calculated from updated research

With integral Solver and 34 steps/wavelength now the maximum gain si around 440 MHz, but as I start the simulation issue occurs: "The minimum mesh quality is very low (6,64e-002). Please consider increase the mesh quality. A better mesh quality improves the simulation time".
How can I get rid of this warning? I tried to increase the mesh but this doesn't change a lot

thanks

Solved,
To increase mesh quality simply there mustn't be too small basic objects with too sharp changes in surface