Longshot here, but...
High humidity can adversely affect the performance of an electrostat. In my experience there's an optimum bias setting for the voltage applied to the panel, and that optimum voltage may change with the ambient humidity. If the bias setting is user-adjustable, that might be something to look at. The bias voltage settings for my SoundLabs decreased significantly when I moved from my barely sea-level home way down yonder in New Orleans to my mile-high-and-dry home in Idaho.
Also, if I recall correctly, the SL-3 combines a line-source-approximating panel with a point-source woofer. Such systems can deliver the best of both worlds, but face a unique challenge: The sound pressure level falls off more gradually with distance from the panel than from the woofer. This can result in the system sounding unbalanced if the combination of listening distance and room acoustics are significantly different from what the designer had in mind. So perhaps even moreso than with conventional speakers, experimentation with speaker and listener positioning is called for... but the good news is, if this is part of what's going on, experimentation is likely to yield significant benefits.
Obviously these are not snare-specific suggestions, and are presented with the usual disclaimers: Imo, ime, ymmv, etc.
Duke
dealer/manufacturer