It's not a bug, just a limitation. The IPC between Tibia clients and XenoSuite can be very heavy, and the limit of 100 exists because of this. Because of the way XenoBot allocates IPC channels, it actually has 100 on stand-by and rotates them out as needed. I didn't really expect anybody to run 100 clients.

If you would like to run more than 100 clients, I'd recommend doing so on multiple VM's (VM's created on the same software with the same Windows image and hardware configs will have idential XB keys).