Daikin unit fault in winter

[TCTBRAD]

Hi I am having some trouble with a daikin split wall mount
Indoor Model : FTXE25BVMA8
Outdoor Model : RXE25BVMA

for probably the last 3 years we have had this unit stopping during winter when reset will go for another month or 2 months then needs resetting again overall probably needs 3 resets to get through winter. summer operation is ok though.

it seems to happen on the coldest mornings we had -5 Celsius the other day which made it stop.
the indoor unit is showing a constant flashing light and the same on the outdoor PCB. The outdoor unit is located on top of a 3 story building with the indoor unit being on the ground floor so a fairly big vertical pipe run for a little unit not sure on the maximum allowed ??

A former colleague was suspicious it was a gas issue so he recharged with the base charge and additional grams per meter but this did not make a difference. I have seen the unit defrost ok ( during slightly warmer mornings ) so I am thinking that the pipe run is to long and the compressor might be struggling during defrost on those extra cold mornings.

anyone heard of this issue ??
any help would be much appreciated

[martinw58]

have had this on units that are under sized thay tend to ice up in the winter

[TCTBRAD]

Looks like we have been asked to replace it now but i would say that would be the issue