Tuning Oticon Own 1 IIC for deep voices

Hello

I’m using Oticon Own 1 IIC and have severe high frequency sensorineural hearing loss.

For some reason, I have most challenge with understanding people with deep voices and not higher pitch voices.
I actually hear them better in noisy environment vs in quiet or open spaces(A distance away) environment. They sound like they’re mumbling in quiet or open spaces(A distance away) environment even when they are near.

Manual adjustments by increasing low freq makes it worse. Manual adjustments by increasing high freq makes it tinny and does not help speech comprehension.

My audiologist have done REM.

Soft speech booster is maxed out with noise reduction in both easy and challenging environment. Speech rescue is also utilised.

Anyone has any idea if there’s a way to improve the tuning?

Thank you.