transmit audio level varies greatly with location in the house

I have SmartSDR for iOS (app version 6.1.3, data version D4.1.40 on my iPhone 11 Pro.

I had hoped to continue to communicate on a 2m repeater by using SSDR on my iPhone after retreating to an interior hallway during severe weather events. Two attempts this week failed due to low or no transmit audio.

I had set up my transmit audio level at home in the living room, using the settings listed in the manual under "Too low Microphone gain." My phone was connectied to a Wi-Fi access point about 6 feet away. I use a 2mLDPA with my Flex 6700 on 2m FM. I used a dual band HT with earphone to listen to the transmission using the iPhone and compared the level with other's transmissions on a 2m repeater. I set it to be roughly equal to the level of the other's transmissions, by ear.

I moved to the hallway about 20 ft away and found the transmit audio level had dropped so much that one might think there was no audio. The RF level was still strong.

I guess this issue is caused by my radio connection in some way.

I have 3 Wi-Fi access points in the house and the Wi-Fi signal is very strong at both locations (Wi-Fi icon at top right of screen is at max). I did a speed test on my phone and in the Living Room the download speed was 476 Mbps and upload speed was 11.7 Mbps. In the hallway, these were 415 and 11.5, respectively.

For the above, my SmartSDR connection was to the FLEX-6700 using the LAN IP address.

I also tried turning Wi-Fi off on my phone, and made the radio connection using SmartLink to the WAN IP address. That had to same result of great tranmit audio in the Living Room and almost non-existent audio in the hallway.

Next I used my iPhone to call my landline and left a voicemail from the Living Room and again from the hallway. There was no discernable difference in audio level. Both were comparable to the audio level of other voicemails.

I am not sure what else to check.

Any help would be greatly appreciated.