Audio tracking falling out of sync

Running ver. 2.1.2 on a Windows 7 machine
I’m having trouble editing to audio files together as after a while (5-10mins) they are noticeably out of sync.
One file is recorded straight into Audacity 44100hz, 16-bit. The other recorded on a portable Tascam - 44.1k hz, 16 bit wave file.

Can anybody help me out as I’d driving me nuts?

Effect > Change Speed. Put the longest two clips on the timeline so you can figure out the difference with the best accuracy.

Audacity 44100hz, 16-bit.

Your soundcard? I believe the Tascam.