Detector rails normally activate for ~20 ticks (depends on how fast the minecart goes) Sometimes though they randomly activate for something that looks like half of that normal time even if the minecart moves with the same speed.
To set up an experiment, create ~ 3x5 loop with some powered rails and a detector rail. Launch an empty minecart. Output the signal from the detector into a line of ~15 repeaters on 1 tick delay. Observe gaps in the output change in size sometimes.
P.S. This might relate to a bug which made a button to sometimes produce a shorter pulse, which I can't reproduce in 1.4.5 so far.
Linked issues
duplicates 1
is duplicated by 4
MC-4173
Buttons occasionally output too short pulse
Resolved
MC-16044
Erroneous Button Output (1tick/5ticks)
Resolved
MC-18450
Sticky pistons, even on a long pulse, will occasionally not retract with the block they are meant to retract.
Resolved
MC-47237
Sometimes buttons will short-press instead of pressing for the normal amount of time.
Resolved
Attachments
Comments 15
Cannot reproduce.
Rebuilt your setup, but there's a discrepancy in your description:
You wrote in the text, the issue would occur with a 3 x 5 loop, but your screenshot shows a 3 x 4 loop.
With a 3x4 loop the output signal of the detector rail is permanently on
Stared for several minutes on the screen, but never saw a shorter pulse on the 3 x 5 loop.
3x4 loop might be always on because of either directional stuff, or the way you start minecart, which is by pushing in your case...
It's still weird that the bug doesn't seem to show up though. I get it consistently in my setup. Should I post the world savefile?
Actually, it is downloadable at http://kimitsudesu.net/files/minecraft/sv.zip
The coordinates are shown on the screenshot.
Is this still a concern in the current Minecraft version? If so, please update the affected versions in order to best aid Mojang ensuring bugs are still valid in the latest releases/pre-releases.
Is this still a concern in the current Minecraft version 1.7.4 / Launcher version 1.3.8 or later? If so, please update the affected versions in order to best aid Mojang ensuring bugs are still valid in the latest releases/pre-releases.
Does this issue still happen in 14w26b? I recently committed a fix that removes random block ticking from redstone devices.
duplicates MC-56541
edit:
and yes its fixed now
Can you please press F3 + C for 10 seconds to force a crash and attach the resulting crash report here ?