The only real solution is process-of-elimination, also known as debugging. This is detective work; it costs time but will certainly find the problem.
The plan is to test each plugin that causes an issue, separated from all other plugins:
1. Move all your normal plugins out of the SC4 folders. Then put
only the AC ARP (plus its dependencies) into plugins.
Dependencies for AC ARP: AC MEGA Props Vol02, AC MEGA Textures Vol01
Start the game,
make a new blank region, load a city and try to plop the lots.
Do not save the city.
2. Next, pull the ARP (and dependencies) out of plugins. Put the SCAG ARIP (and dependencies) into plugins.
Dependencies for SCAG ARIP: AC MEGA Props Vol02, AC MEGA Textures Vol01, AC MEGA Textures Vol02
Load the game and test-plop somewhere in your blank region.
Do not save the city.
3. Pull the ARIP & dependencies out, and test the SCAG TMIP with its dependencies.
Dependencies for SCAG TMIP: AC MEGA Props Vol02, AC MEGA Textures Vol01
Test-plop again in the blank region.
Do not save the city.
With these tests, the packs are being tested independently. If one fails, then the problem is found... let me know how it goes
