The situation you describe sounds normal apart from it going immediately back to red LED.
This will happen if the mains 230 volt supply is interrupted, even only briefly.
Did you unplug the mains or was it switched off at all ?
This has the effect of starting the charging process from the beginning again, i.e. red, amber, green LED.
If it was switched off the 5 amps you refer to is not unusual, either the restart of the charging phase, or if fully charged, simply trying to replace what you are drawing from the battery at that moment in time. Was the heating on for instance or were there some lights on. Hopefully it was showing 5 amps positive charge on the ammeter.
When the LED is green this is the ‘trickle charge phase’ and also the time that the output from the charger is directed to the engine battery.
During this time the engine battery will be charged, assuming that all fuses and wiring are intact.
The fuses I refer to are one external to the charger and one adjacent to the engine battery. The one adjacent to the engine battery is almost always a big red maxi-fuse in a holder. This fuse and holder next to the engine battery can be subjected to moisture and has been known to prevent the charging of the engine battery.
Hope this is of some help