Just helped someone configure two of these in parallel 120/240V operation, and he experienced something similar.
Prior to final configuration, the unit behaved as the OP described. After reconfiguration and the complete hard "reboot" necessitated by wiring changes that completely disconnected the units from all sources, proper operation has initiated:
Bulk to bulk
Hang out there awhile.
Drop to float.
Hold float and power loads with solar.
IMHO float should not be above 27.2 as floating them above 3.4V/cell is never recommended and can damage cells.
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