Bright/Dim commands are a special case for repeaters. X10 signals are normally sent twice in the same message. Most repeaters take advantage of that by receiving a command during the first half, and re-transmitting it in exact sync with the second half. This works for most commands where a module only needs one valid copy to take action.
Bright/dim commands work differently. There are normal bright/dim steps, which will slew the dimmer from full-on to full-off in about 16 steps. Then there are micro-dim steps, which take over 100 from full-on to full-off. Unfortunately, the X10 protocol uses exactly the same command for both. The only way the receiving module can tell them apart is how they are strung together.
Normal bright/dim commands are sent in sequence with no gap between. A sequence of several bright/dim commands sent that way will ramp a light quickly. The repeater messes up this sequence by only repeating the second half of each bright/dim command. So those bright/dim commands are recognized as micro-dim steps by any module that does not receive the first half. Some repeaters have a fix for this, and it is one of the special cases I am trying to handle in the repeater version of the XTB-II.
A suggested fix is to move your transmitter closer to the main distribution panel so the modules stand a better chance of receiving the first half of the bright/dim message. If that is not feasible, you could use a booster to directly increase the transmitter output.
Jeff