When rails are activated via redstone signal repeatedly, as soon as a redstone signal activates adjacent rails, if their redstone signal source is present, even if deactivated, the rails in question activate anyway.

Video below

Steps to reproduce:

1. Bild a (at least) 16 block long powered rail line ;
2. Activate the rail line from one end repeatedly * - when done, the block used to activate must be placed with no redstone signal being sent ;
3. Place a redstone source (Redstone Torch, Redstone Block, etc.) 16 blocks away from the original power source.

*It can be done mannually, or with a redstone clock. It also happens when a Redstone Repeater, receiving the signal from a redstone clock, sends the signal continuously, without deactivating, due to the chosen delay mode.

Expected results:

Rails up to 8 blocks away from the second source are activated on both sides.

Results:

All 16 rails between the two power sources - the first one being on and the second one being off - are activated.

If the block used as the first power source is broken, it goes back to normal, however if the same block is replaced, even with no aditional activation, and the second power source is removed and replaced, all 16 rails are activated again.