The problem is certainly not that you have too many routes or that your system specs are not good enough. :)
The AI is quite passive most of the time, this is something we will fix in one of the upcoming versions.
I will release a patch later this evening (CET time) that might fix the issue. Sadly, it won't fix your save, sorry.
If it doesn't fix the issue, can you give me the crashlog? You can find it in the rootfolder called 'TAPv2.log'.
Thanks for reporting!
Edit: I went ahead and pushed the patch already. :)