vaseline can swell . When I worked at silva Uk making GPS handheld units the R&D guys would put vaseline on the o-rings to swell them to see if I thicker o'ring would work if they did not have thicker ones in the stores.
It depends on the makeup of the seals. If you have a spare seal then try it with petroleum based oils or grease and see if they swell up.
You could try forte lubricants and see if they will send you a sample of their one https://www.forteuk.co.uk/product-de...al-Conditioner tell them if it works you will startbuying it buy the case
a thread here on swelling O-rings https://www.bobistheoilguy.com/forum...Number=1854960
Maybe a rebuild will be the best way all round though as you could end up swelling seals that don't need to swelled and cause more problems .