Items most times not visible in rules or PaperUI


in my item file I have more than 100 item working as expected, but a few number items for szenes are not visible in PaperUI or working in rules.
The funny thing is that in 1 out of 4 cases after a reboot of the system or restart of openhab the items are visible and working.

Extract of the items file

Number Thermometer_Garten_Temp_Min “Garten Minimum heute [%.1f °C]” (gGarten)
Number Thermometer_Garten_Temp_Max “Garten Maximum heute [%.1f °C]” (gGarten)
Number Thermometer_Garten_Temp_MinW “Garten Minimum Woche [%.1f °C]” (gGarten)
Number Thermometer_Garten_Temp_MaxW “Garten Maximum Woche [%.1f °C]” (gGarten)
Number Thermostate_Szene “Thermostat Szene [%d]” (gThermostat)

Example of a rule

rule “Min Max Temperatur”
Item Thermometer_Garten_Temp changed or
Time cron “0 0 0 * * ?”
postUpdate(Thermometer_Garten_Temp_Max, Thermometer_Garten_Temp.maximumSince(now.withTimeAtStartOfDay).state)
postUpdate(Thermometer_Garten_Temp_Min, Thermometer_Garten_Temp.minimumSince(now.withTimeAtStartOfDay).state)
postUpdate(Thermometer_Garten_Temp_MaxW, Thermometer_Garten_Temp.maximumSince(now.minusDays(7).withTimeAtStartOfDay).state)
postUpdate(Thermometer_Garten_Temp_MinW, Thermometer_Garten_Temp.minimumSince(now.minusDays(7).withTimeAtStartOfDay).state)

In openhab rules I see the following Error

2020-10-20 07:23:55.229 [DEBUG] [ntime.internal.engine.RuleEngineImpl] - Executing rule ‘Min Max Temperatur’
2020-10-20 07:23:55.246 [ERROR] [ntime.internal.engine.RuleEngineImpl] - Rule ‘Min Max Temperatur’: The name ‘Thermometer_Garten_Temp_Max’ cannot be resolved to an item or type; line 22, column 13, length 27

In the events.log I found no entry with the Min / Max or Szene items

Im running openhab 2.5.9 on a BananaPi M2U with armbian and all updates.

Any Ideas ?

Thank you

This is a perennial problem for some users, some workarounds here -

Thank you for the answer, but I won’t work after testing some of the points

This Morning all Szene and Min/Max Items are visible and working without doing something over night - spooky