I’m still using the original Roku Tablo app, and noticed fast forward will get stuck after clicking the OK button around 25% of the time.
I also skip back, and forward again to get the spot I wanted.
I haven’t had a Roku reboot in 4 weeks, and this coincides with this workaround for fast forward loading getting stuck.
I’ll try pressing the Play button, like @philsoft mentioned to see if the loading hang goes away completely.