Schools in Guangzhou (I cant speak for other cities in Guangdong) are very particular about obtaining a copy of the last applicable F.E.C. of any foreign teacher who has previously worked in China. After becoming aware of this, I made it a habit to always obtain a photocopy of my F.E.C.s (schools insist on retaining the originals).

Anyway, I went through a similar situation to you except that I actually began working at the new school before they asked for a copy of my F.E.C.. My new school asked for it within 3 or 4 days of me starting work.

I told the school that my former school had obtained an F.E.C. for me but I was never given a copy. My new school contacted my old school to ask for a copy. The latter told the former that I had breached by contract and therefore they would not cooperate.

My new school went ahead and applied for a new F.E.C. for me with the Foreign Experts Bureau, and got one. The F.E.B. obviously saw my passport (I seem to recall that they had it for 3 to 4 days), which contained an unexpired Residence Permit naming my former school as my employer.

With a new F.E.C., I thought everything was resolved. However, when my new school went to the PSB to have my R.P. changed over, the PSB requested a release letter from my old school. The PSB held my passport pending receipt of a Release Letter.

My new school requested the said letter from my old school but they refused. My new school then went back to the F.E.B. who contacted my old school. The F.E.B. later directed my new school to pay a 4,000 RMB breach of contract penalty to the old school. The F.E.B. said that if the old school did not provide a Release Letter within 7 days of payment being made, my new school should revert back to the F.E.B.

Payment was made, a letter was provided within 3 days, the letter was taken to the PSB and my passport, containing a replacement R.P. was returned.

The FAO at my new school told me that the PSB told him, having successfully obtained a new F.E.C., I should have gone to Hong Kong to get a new Z visa which would have been converted to a new RP without reference to my former school.

Tell your prospective new school that your old school has / had an F.E.C. but you were never given a copy. Your new school will contact your old school to ask for a copy. Maybe the old school will cooperate in which case you wont have a problem. If your old school wont cooperate, you will have to deal with them yourself and try to resolve the issue.

Not much else you can do whilst your RP remains current.