Quick background... I've used Mikrotik routers for a while, but this is my first major wireless effort (and a long-distance bridge at that)!

I have a NetMetal 5SHP triple connected to a mANT30 PA on both ends of a wireless bridge. I used this tutorial on YouTube (https://www.youtube.com/watch?v=QIp9jfABZFY) to help get the radios configured from an empty configuration. Things worked well in our workshop tests, but now that we have them at their locations 1.56 miles apart (2.51 km) we're experiencing high packet loss when I run the bandwidth test.

The sites have a clear line-of-sight (even in the Fresnel zone), but we attempted to re-peak them twice today and didn't get any improvement.

Looking at the CPE end, my Tx/Rx signal strength is shown as -41/-48 dBm and my Tx/Rx CCQ varies quite a bit -- sometimes around 70/90% peaking at 90/94%. My SNR is 49 dB.

The only change I made from the video is that I selected chains 0 and 1 (since it's a triple chain radio and only a dual chain antenna) and added a WPA2 key to secure the bridge.

Thanks in advance for any assistance you could provide!

You do not mention doing any kind of survey for other 5GHz stuff in the air. This should be done from both sides to find a clean channel.
Also, the video says 80MHz channel... You should try to get a stable 20MHz link first, and then try to get 40MHz stable if needed.