Strange behaviour with parallel timers - please verify it - timers not thread save?

Setup, Configuration and Use Scripts & Rules
1

I run into a very strange problem, can anyone verify this please.

If two or more timers will end on the same time, not all of them are executed:

This works:

var Timer tRandomTimers01 = null
var Timer tRandomTimers02 = null
var Timer tRandomTimers03 = null
var Timer tRandomTimers04 = null

tRandomTimers01 = createTimer(now.plusSeconds(2),
[|
            logInfo("TIMERCHECK", "RandomTimer for Item " + swRandomTimer01.label + " reached end. Action OFF executed.")
            swRandomTimer01.sendCommand(OFF)
])  

tRandomTimers02 = createTimer(now.plusSeconds(4),
[|
            logInfo("TIMERCHECK", "RandomTimer for Item " + swRandomTimer02.label + " reached end. Action OFF executed.")
            swRandomTimer02.sendCommand(OFF)
])  

tRandomTimers03 = createTimer(now.plusSeconds(6),
[|
            logInfo("TIMERCHECK", "RandomTimer for Item " + swRandomTimer03.label + " reached end. Action OFF executed.")
            swRandomTimer03.sendCommand(OFF)
])  

tRandomTimers04 = createTimer(now.plusSeconds(8),
[|
            logInfo("TIMERCHECK", "RandomTimer for Item " + swRandomTimer04.label + " reached end. Action OFF executed.")
            swRandomTimer04.sendCommand(OFF)
])

Log:

2018-02-24 13:24:49.118 [INFO ] [se.smarthome.model.script.TIMERCHECK] - RandomTimer for Item RandomTimer01 reached end. Action OFF executed.
2018-02-24 13:24:51.118 [INFO ] [se.smarthome.model.script.TIMERCHECK] - RandomTimer for Item RandomTimer02 reached end. Action OFF executed.
2018-02-24 13:24:53.118 [INFO ] [se.smarthome.model.script.TIMERCHECK] - RandomTimer for Item RandomTimer03 reached end. Action OFF executed.
2018-02-24 13:24:55.117 [INFO ] [se.smarthome.model.script.TIMERCHECK] - RandomTimer for Item RandomTimer04 reached end. Action OFF executed.

But this not, only difference is timer will end on the same time:

tRandomTimers01 = createTimer(now.plusSeconds(2),
[|
            logInfo("TIMERCHECK", "RandomTimer for Item " + swRandomTimer01.label + " reached end. Action OFF executed.")
            swRandomTimer01.sendCommand(OFF)
])  

tRandomTimers02 = createTimer(now.plusSeconds(2),
[|
            logInfo("TIMERCHECK", "RandomTimer for Item " + swRandomTimer02.label + " reached end. Action OFF executed.")
            swRandomTimer02.sendCommand(OFF)
])  

tRandomTimers03 = createTimer(now.plusSeconds(2),
[|
            logInfo("TIMERCHECK", "RandomTimer for Item " + swRandomTimer03.label + " reached end. Action OFF executed.")
            swRandomTimer03.sendCommand(OFF)
])  

tRandomTimers04 = createTimer(now.plusSeconds(2),
[|
            logInfo("TIMERCHECK", "RandomTimer for Item " + swRandomTimer04.label + " reached end. Action OFF executed.")
            swRandomTimer04.sendCommand(OFF)
])

Log:

2018-02-24 13:31:09.089 [INFO ] [se.smarthome.model.script.TIMERCHECK] - RandomTimer for Item RandomTimer01 reached end. Action OFF executed.
2018-02-24 13:31:09.104 [INFO ] [se.smarthome.model.script.TIMERCHECK] - RandomTimer for Item RandomTimer04 reached end. Action OFF executed.
2

I’ve done some more investigation on this:

It looks like this is the missing part. If I add this to the rule all works fine, don’t know why. Maybe someone can tell me.