Double Issue with AME 17 & 18 - MTS file issues

Issue 1:

I shot a 2-hour live performance on a Sony AX2000. It records in MTS. I drop the files into AME 2018 and stitch them. I export the files into h.264 with a medium bit rate. When I watch back the exported file, the audio gets more out of sync the longer the video goes on.

To try and work around this, I installed AME 2017...

Issue 2:

When I export the same MTS files into a stitched MP4 file, I lose audio. I get an error message when I import that says I need to install a Dolby Codec and that will happen if I click OK, but still no audio.

I have another machine that does not have this issue with 2017 (this machine does not have 2018 installed), but I would like it to work properly on my primary machine.

I have tried clearing Media Caches and resetting preferences and restarting the machine and reinstalling the software. Nothing works. Any ideas?

Primary machine where neither 17 or 18 work specs: Mac Pro (Late 2013) v 10.13.5, 3.7 GHz Quad-Core Intel Xeon E5, 64GB 1866 MHz DDR3m, AMD FirePro D300 2048 MB.

Secondary machine where 17 works (18 not installed): iMac (27inch, Mid 2011) v 10.12.6, 3.4 GHz Intel Core i7, 16GB 1333 MHz DDR3, SSD, AMD Radeon HD 6970M 2048 MC