In fact, I notice that this happens not only in redwood forest

You can unzip the mod and go to the folder: assets/ambientsounds/basic/regions. In the regions "cave.ambience" and "cave.lush" (.json files) replace "min-height-relative" with "max-height-relative".

This would solve the problem only for me, but it would leave this problem in the mod itself.

Unfortunately yes.

Thanks for reporting this issue. Sorry for the late response. The issue should be fixed in the newest version.