Extremely slow loading of multiple-track kml files

I've been a happy Locuser for years now. I'm usually cautious about updating any apps too often if they work fine. I had been using an older version of Locus for some time now, probably 3.50 or something, but recently had to wipe my phone completely empty.

After installing everything again, I went for Locus 3.70.9 that was the newest version at the time.

One of my primary uses for Locus is tilehunting (Veloviewer, Squadrats etc) and the personal missing tile files we collect, can be loaded from example veloviewer.com to cover a custom defined area. I would traditionally usually load kml files including around 800-1500 tracks, since any more of them displayed on a map would make Locus a bit sluggish and loading and displaying those tracks would take a slightly longer time. Anyway, those 800-1500 tracks would usually load in mere few seconds, and hiding them all would take maybe one second. The tracks in a kml are always similar square-shaped and have just five points each, so pretty simple. The size of the tile depends on latitude and they are exactly OSM zoom level 14 size, so at this latitude roughly a square kilometer each.

Anyway, after the factory wipe and installing 3.70.9, the loading turned much, much slower. I just timed displaying a 1471 track kml file, and loading it took a whooping 6 minutes and 27 seconds (3,8 tracks per second) Turning it off took 21 seconds.

Another Locuser friend of mine is using 3.70.10 and for her, a 2936 track kml file (double the amount of tracks compared to mine) of tiles would load in just 10 seconds (293,6 tracks per second), and hiding them all in just one second. So comparing to her Locus, mine is 40-80 times (!) slower, even though my phone should be faster (if I understand correctly)

I'm running Android 11 on a Sony Xperia 5 II (Snapdragon 865), and my friend is running Android 14 on a Sony Xperia 10 V (Snapdragon 695).

Any suggestions as to what might be the reason and how to fix it? Do I just have something wrong in the settings (which were a backup from my old 3.50(?)) ? Since my friend has her 3.70.10 and the loading times are perhaps even better than what I used to have earlier on the old version (which were totally fine) on my same phone and same Android version, older versions might not fix this? Or did something happen during the phone wipe? Is there something about how the user's map and track data is stored in the phone / sd card?

I'm attaching a 1471 track kml file (320 kB) for testing and timing etc, if you want to try. Should not take 6 min 27 secs to just display it, right?

Thanks for any help!