Tyre flat spotting?

[Spare tyre]

This evening I purchased a little Erde 102 trailer from gumtree for a bargain price

It needs a tidy up and re wire but it's nothing tricky

I plan to use it for some diy task then will re sell

On the way home it was vibrating really badly at about 50, so much so I came off the motorway to double check it all

I inflated the tyres to the correct pressure but it made no odds

It had been sat for at least a year, so could a flat spot be at play here? Does simply using it resolve flat spot issues?
Thanks

[Watchman]

Over inflate them if there is a flat spot.

I had one and didn't notice when I was cruising at 105 so I know they can be really good.

If you need a new hub bearing, they're only a fiver and really easy to fit.