Charging at 3-4 Amps won't do those little cells any good - it would be like charging 3300's at 9-12A!
So you may have damaged them already.
The v6 is a clever charger - much more so than the Superbrain.
That V Too high reading, as you know, shows the pack voltage is too high under charge - that shows a cell with a lot of internal resistance, or even damage.
What you could do to try and solve are a couple of things. First is to set the charger up as 6-cells to "fool" it into thinking the pack voltage is normal. Second is to discharge that pack at about 1A, this may reduce the inintial voltage under charge.
Or the clips are too chunky to fit on the rx pack connection, I would build up a better adaptor with an rx socket.