Voltage mismatch from parallel connected Lithium Smart batteries

I’ve got 2x 25.6V 200Ah Victron Lithium Smart batteries connected in series, with another identical pair connected in parallel with them (i.e. 2S2P arrangement). They are connected to a thick copper busbar. The Victron Connect app reports the voltages of one series-connected pair as 52.04V (26.00 + 26.04) and the other pair as 52.34V (26.17 + 26.17). I’ve measured the voltage at the terminals with a multimeter and they both read 52.3V. It seems like the voltage reported by the BTV module in one pair of batteries is not quite accurate. Is there a way to recalibrate this?