Blistering and delaminating boards

Has anyone else been experiencing this lately? We have had a rash of boards that come in properly vacuum sealed. We store them in the hot room until we are ready to build, and we get bubbles under the solder mask.

We've had 4 different jobs, all different customers, do this. Three of them are customer supplied boards, that we have been building for years. The one that we purchase has already been sent to our supplier for evaluation.

I'm talking 3-6 boards out of 200. Though one customer it was every board they supplied for an order. After the first few, we pre-baked 50 of the boards. The next 5 still delaminated.

All are RoHS boards, most are ENIG.

Has anyone else seen an increase in this issue in the last couple months?

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