2016 Platinum, cranks over and won't start, sporadically.

I have a 2016 Platinum Tundra.
I have a viper 2-way 5806 and Smarstart.
- It has been working fine for over a year

Recently, it started sporadically just cranking over and not starting the vehicle. Sometimes it works fine, sometimes it cranks over for 10 seconds, then starts the process again. Sometimes it cranks on the second time, sometimes it doesn't. Generally after a failed sequence, it will start

Most of the time I start the vehicle with the remote start. On two occasions when I was experiencing the remote start failure, i used the key, and it just cranked over as well, without starting.

I took it to a viper installer who replaced the brain, and reviewed the wiring. It seemed like it was fixed. It started failing again the next day.

When it does crank after these failures, the exhaust does smell bad; Not like raw fuel but a concentred, distinct and foul smell.

This issue appears to happen after the vehicle has sat for some time and particularly in the morning / night, when it is cooler out.

Any help, thoughts, or suggestions would be greatly appreciated. Given the key seems to have the same issue as the remote start, it may be unrelated to the remote start, but that seems unlikely.