From the post, I'm not sure if you have an antenna analyser or are just using an SWR bridge. If you dont have one and can borrow an antenna analyser (perhaps from your local club), I would advise that rather than just trying for the lowest SWR on 40m just with an SWR bridge and expecting the other bands to be correct. Perhaps there were two dips near 40 metres and you trimmed to the wrong one. With an antenna analyser, especially a graphical one, you can see better what you are doing and by scanning all the way from 40m to 10m, you can see what changing the length of the antenna might do on all bands.
I would also check with the manufacturer whether they expect the antenna to be in a specific configuration while tuning to resonance - perhaps they don't expect the antenna to be in a sloper configuration, for example. It's likely that the type of ground, the height above the ground, other things in the area to the antenna will affect the antenna. Setting up the antenna one one summit will give different results to on a different summit, that's life. If you are not simply going to use the antenna at the home QTH, this is something you have to accept. Anything under 2:1 or ideally 1.5:1 in a portable set-up is a good result.
73 Ed DD5LP.