This could be due to one of several reasons.
Self-consumption mode:
Near the top of the state of charge range (80-100%) the maximum battery charge power is reduced to preserve battery life.
For cold or warm temperatures the battery will limit its charge & discharge power.
Duracell normal operating range is 20C - 40C.
SolaX X1 AC operating range is 5 - 45C
Optimisation mode:
Optimisation service may be limiting the amount of PV absorbed to ensure the battery is available for other, higher paying services. This is entirely normal and is exactly what we would expect your system to do.
For technical support about your system please contact support@levelise.com