Wrong and also failed transcoding for KV operations

After migrating to nodejs client v4.1.0 we observe the following behaviour:

Previously existing documents are failing the decoding for KV operations done by the DefaultTranscoder. The following line seems to have no effect.

return JSON.parse(bytes.toString('utf8')); 

Furthermore we are observing errors while trying do the encoding for some documents. A document with some unicode content cannot be transformed at all:

The JSON.parse fails with SyntaxError: Unexpected token in JSON. This leads to returning the content as Buffer.

We've tried to register a custom transcoder but have failed to fix this behaviour somehow. It seems that the input buffer is already corrupted.

NQ1L operations are working as before. There we cannot see any issues regarding transcoding.