If we bought a bar 5 months ago from the bank, can the previous owners now try to remove things?

Anything which was included in the sale of the bar, they clearly cannot remove; that would include anything listed as an inclusion on the contract of sale or anything which is a fixture--e.g. attached to the premises.

As to anything not listed as an inclusion, or not a fixture (e.g. a jukebox; a television)

If the owners clearly abandoned belongings--e.g. by indicating or stating that they did not want the items; or by not responding if you reached out to them and asked them to remove anything they wanted--they would have no right to those items.

After five months, it *may* be the case that even in the absence of a clear indication of abandonment, that they could be considered to have abandoned the items--you could raise a good argument that was the case, but it's simply not as certain as if there had been an expression of abandonment. Just be aware that if there was no expression of abandonment and no agreement (e.g. in the contract of sale) that you could keep these things, the former owners might be able to claim ownership still--much depends on the specific factual circumstances. So if this is the case, and if it appears that the former owners would be willing to sue for  these items, you would need to decide whether they are worth litigation, given that even if you would have a good case, it is possible you would lose.