signrawtransactionwithwallet seems to break the existing signatures of some of the inputs

It seems that this rpc alters the scriptSig of all of the inputs that were already signed (second and third vins in this case), except for the first one.
This is an example with 4 inputs, where the first 3 are transactions that are already signed:

Before executing signrawtransactionwithwallet, I have this transaction:
```
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
```
and after executing it, I get this one:
```
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
```

By decoding both, it seems that this RPC alters the scriptSig of all of the inputs that were already signed, except for the first one.

The error that is returned by the RPC on the inputs that were already signed (second and third vins in this case) is:
"Unable to sign input, invalid stack size (possibly missing key)"

Beginne damit, das Problem mit den bereitgestellten Raw-Transaktionen vor und nach der Änderung sowie dem signrawtransactionwithwallet RPC zu reproduzieren. Untersuche anschließend, wie bereits signierte Inputs behandelt werden, wenn ein anderer Input signiert wird. Die Aufgabe ist abgeschlossen, wenn vorhandene gültige scriptSigs unverändert bleiben und das RPC für diese Inputs keine Meldung über eine ungültige Stack-Größe mehr ausgibt.

Vom Indexierungsmodell aus dem Issue-Text verfasst.