hey whats up?

i found solutions to my other problems and can author a dvd with subtitles. However i have a new one and their is no reason why it should be doing what it's doing:

i add in my made subittle track (bitmap pic, not a dvd rip) i set it for an on and off using the buttons on the menu( oh the subtitle is set to play the full lenght of the movie). I play the authored dvd on my hardrive. I turn on the subs, they work, i turn off the subs they work. HOWEVER, if i fast forward/rewind or skip a chapter the subs dissappear and then they refuse to turn back on again. i then tried the disc in 2 homedeck machines with the same result. if anyone can help me it would greatly be appreciated, need any help asap. thanks again---