Volume always set to -40 when switching to VAR (line out + headphone)

VAR/FIX button behavior changed:
1.         FIX – Line Out: FIX; HA - Not active, LED: off        
2.         VAR – Line Out: MUTE; HA -  Active, LED: slow blinking        ...volume HA forced  -40 
3.         VAR – Line Out: VAR; HA - Not Active, LED: on        ...volume VAR forced  -40

Short VAR button press: switch from 1->2 and 2->3
Long VAR button press: switch from 3->1


Update Instruction for Windows PC:
1. Install Audio Driver from MF website or from M8x DAC FW Update .ZIP file "UNI_Project_v6.16.0_2026-06-08_setup.exe"
2. Connect M8x DAC via USB to PC
3. Open ds2wDfu.exe from M8x DAC FW Update Folder "Firmware Update Utility"
4. Load m8x_dac_upgrade_stm103b.bin
5. Start FW Update
6. When update is finished, power cycle M8x DAC