Hornby GWR 4-4-0 service

[stonesfan]

Hi All

Giving my Hornby 4-4-0 GWR County of Bedford some TLC. Have greased all the gears, have new tyres on order. Tender runs really quietly and smoothly when you connect test cables to the motor. However the issues are that it runs erratically once connected to the main chassis. The con rods are all lightly greased and move freely. Possibly points to something electrical? Have cleaned and firmed up the two brass contacts that connect the tender hook. Also....and whether I'm right to do this, put a couple of tiny drops of Peco electrolube on the brass contact hook too. Presume that's what it's for or am I getting it totally wrong?! Still runs erratically after doing all this. Anything else I need to look at?

Thanks again