Greetings,
I think that this will become a regular problem in the future as the 'new' petrol contains additives that attacks plastic and grp type components.
It is a good service point to check these filters perhaps once a year any way as they can become blocked as with any filter/tap in an open line refuelling context. I recently replaced the tap on my Beta Alp 4.0 for one with a reserve feature so that I would be alerted to low fuel before the inevitable running totally dry.
I bought my replacement tap from Steve Goode and received excellent service so perhaps make enquires for a suitable replacement through his company,
http://stevegoodemotorcycles.weebly.comYou could just fit an inline filter as previously suggested.
TTFN
Hugh.