Problem description: there are issues with changing item value type - for example if a trapper item with preprocessing (int values replaced by strings) had value type "Numeric unsigned", value was sent and item became unsupported, then when the value type is changed back to Text and a new value is received, the item remains unsupported. In both cases config cache reload was performed before sending data to the item.
This behavior doesn't occur every time when for the above described scenario, so maybe multiple attempts will be needed to reproduce the problem. At least it reproduces more or less stable if server is restarted before executing the above scenario.

Steps to reproduce:

1. Restart zabbix server
2. Create a trapper item with Value type = "Numeric (unsigned)" and the following preprocessing steps:
   1. Replace "0" => "BAD"
   2. Replace "1" => "GOOD"
3. Send value "1" to the item - item became unsupported
4. Change item type to Text and reload configuration cache
5. Send value "0" to the item and check item state

Result: item is still unsupported, the error indicates that item cannot process string item as its value type is Numeric (unsigned)
Expected: in reality item type is Text, therefore it should process string items without any issues

Log file: zabbix_server_old2.log
Item ID in log file: 44582