Your security software blocks the trainer from creating a tmp file in the Work folder which is located here -> C:\Users\YourWindowsUserName\Cheathappens\
Create a scan exclusion for this folder, clear your security software's quarantine and scan logs, the Windows Temp folder, reboot your PC and try again.
[Edited by HollowSCV, 7/8/2018 10:25:52 PM]
About option Numpad 2 Unlimited Ammo: '...Works with most weapons and weapon addons. May not work with all.' - this means that the first weapon function (ie Charged Burst for the shotgun) is supported but not the second one.
Did you read and followed the steps described in the trainer's instructions for optins like Weapon and 99 Tokens currency?
I downloaded the game from Steam and our latest trainer and all options are working as intended. I can ALT+TAB to Desktop and go back into the game without a crash or any other problem. Either you need to verify the game cache or uninstall, reboot and install the game and try again.
I will try doing as you said.