Assertion failed: rd_slice_abs_offset

Description
===========
While reading data from a consumer and writing to a sink I get the following error:

`Assertion failed: rd_slice_abs_offset(new_slice) <= new_slice->end (rdbuf.c: rd_slice_narrow_copy: 1027)`

No additional information is provided. One thing I've noticed is that the message is not always the last one. I've upgraded the client and librdkafka to 1.2.0 and this is still occurring.

Thank you

Checklist
=========
Please provide the following information:

- [ ] confluent-kafka-python and librdkafka version (`confluent_kafka.version()` and `confluent_kafka.libversion()`):
- [ ] Apache Kafka broker version:
- [ ] Client configuration: `{...}`
- [ ] Operating system:
- [ ] Provide client logs (with `'debug': '..'` as necessary)
- [ ] Provide broker log excerpts
- [ ] Critical issue