Thanks @ericmartinpe, your suggestion got me closer to the solution. It's a little different.

All that happened was that the EMS did not have a check for when the Eco parameter became negative which was likely causing the fan pressure to be negative under extreme conditions. To fix that I simply set Eco to 0 when Program Line 36 causes a negative value (see updated Github Link correction)

Thanks @ericmartinpe, your suggestion got me closer to the solution. It's a little different.

All that happened was that the EMS did not have a check for when the Eco parameter became negative which was likely causing the fan pressure to be negative under extreme conditions. To fix that I simply set Eco to 0 when Program Line 36 causes a negative value (see updated Github Link Link correction)