When using SMPTE timecode in a Firelinx show, if experiencing issues, the first thing to do is to double check the frame rate of the SMPTE output and make sure that Firelinx is configured for that frame rate. Firelinx supports 24, 25, 29.97, and 30fps SMPTE rates.
You can easily check and modify Firelinx’s SMPTE frame rate in the SMPTE menu from the settings menu.
From there you can select the frame rate that properly matches your SMPTE output. If you are unsure what your SMPTE frame rate is, run SMPTE while in the menu and watch the time tick in the menu and see if there are any skips in time. If the time skips the frame rate is likely inaccurate and should be adjusted.