What are you using for a midi device? Do you have the newest drivers for it? Are you running a lot of midi data?
There is a problem that sometimes arises with midi called midi slop which is when the timing of notes and clocks and other messages in a midi system slow down and get off. It used to be a bigger problem with older devices and computers that had less processing power, but it can still happen depending on the circumstances. A couple things to try would be to restart your machine, try running less midi data through your interface, or finally use TF as a midi device connected through your computers usb port as opposed to through a midi device.
Finally since TF is a delay and not a drum machine or synth. If your track stays at 90 bpm the whole time and you set TF to 90 bpm it doesn't actually need to recieve the clock to stay in sync. As long as the delay time is set correctly the output will follow the input regardless of the beat number.