let me see if I can explain this. there are 2 ways of getting lockup in manual forward gears one way allows lockup in 2nd manual and above and the other allows lockup in all forward gears. since you had 2nd through 4th lockup your valve body has 2 holes in the overdrive seperator plate plugged, converter timing valve and spring flipped, and a .110" hole drilled through the lower housing, so my guess would be that whatever your builder used to plug the holes in the seperator plate has come out, because you still have lockup in 3rd which a factory valvebody will allow. I would put money on a plug has come out. I hope I was helpful and somewhat clear.