The delays are nothing new.

For many years there have been notices on the Gib side, where the cars queue to leave, requesting people to contact the EU to complain about Spain's behavior, seems to have achieved nothing.

Since the border was re-opened in 1985 (having been closed for 16 years by Franco in an attempt to make Gib submit) there have been many times when the queues leaving Gib have been artificially delayed. Often it seems to also happens in the couple of weeks leading up to Christmas, believed to be to discourage expats doing their ‘Christmas shopping’ on the rock.

I don’t visit that often now (as my wife is Filipino and thus needs a visa to enter. However, I recently discovered I can get around that as I have dual nationality, and as long as I do not disclose that I have British nationality along with Irish, she can enter without a visa as the spouse of an Irishman). On the last couple of visits when we returned across the border to Spain, the Spanish immigration control officer was reading a book and waving the line of cars through without even looking up.
When they decide to slow it down, they walk around the cars as slowly as possible, demanding every piece of paper drivers should carry, examining them as slowly as possible, looking into the boots, bonnet, under the seats etc. Not with any thoroughness, just slowly.

Maybe about a year ago, the mayor of La Linea (the border town) started constructing new traffic ‘barriers’ to start charging cars to enter Gib (the congestion is a real problem for the town and must cause substantial cost) but the Spanish government stopped her as they said it would be illegal.

I know there is an argument that Gib is Spanish as it is part of the Peninsula, but then so are Portugal and Andorra and France has a border too, so where would that argument stop?

Spain has two enclaves in Morocco which to everyone but the Spanish appear to part of Morocco but despite requests they will not hand them over. Kettle and Pot comes to mind.