xDAI stuck on GC (with 3 signatures)

Hello,

It looks impossible to claim funds on mainnet for this bridge initiation: 0xd6885a8f5e0ef79a332711a594763005ae2726c9cee9196e41617c989708b044

It has been executed 2 months ago, with 957 xDAI locked. It looks like the number of required signatures has been increased last week form 3 to 4 (Ethereum Transaction Hash (Txhash) Details | Etherscan) so how do I get an additional signature?

Thank you in advance for your help.