md5checksum shows example dataset analysis fails

Hi, I've been trying to use dentist on the provided example dataset but a number of the md5 check sums after it finishes running are failing with no other errors that I can find.

I installed snakemake v6.0.0 and singularity v3.6.3 through conda and ran through the example dataset as follows:

```
wget https://bds.mpi-cbg.de/hillerlab/DENTIST/dentist-example.v1.0.1.tar.gz
tar -xzf ./dentist-example.v1.0.1.tar.gz
cd dentist-example

# run the workflow
SKIP_LACHECK=1 snakemake --configfile=snakemake.yaml --use-singularity --cores=4

# validate the files
md5sum -c checksum.md5
```

but the checksum output was as follows:

```
gap-closed.fasta: FAILED
workdir/.assembly-test.bps: OK
workdir/.assembly-test.dentist-reads.anno: OK
workdir/.assembly-test.dentist-reads.data: OK
workdir/.assembly-test.dentist-self.anno: OK
workdir/.assembly-test.dentist-self.data: OK
workdir/.assembly-test.dust.anno: OK
workdir/.assembly-test.dust.data: OK
workdir/.assembly-test.hdr: OK
workdir/.assembly-test.idx: OK
workdir/.assembly-test.tan.anno: OK
workdir/.assembly-test.tan.data: OK
workdir/.gap-closed-preliminary.bps: FAILED
workdir/.gap-closed-preliminary.dentist-self.anno: FAILED
workdir/.gap-closed-preliminary.dentist-self.data: FAILED
workdir/.gap-closed-preliminary.dentist-weak-coverage.anno: FAILED
workdir/.gap-closed-preliminary.dentist-weak-coverage.data: FAILED
workdir/.gap-closed-preliminary.dust.anno: FAILED
workdir/.gap-closed-preliminary.dust.data: FAILED
workdir/.gap-closed-preliminary.hdr: OK
workdir/.gap-closed-preliminary.idx: FAILED
workdir/.gap-closed-preliminary.tan.anno: FAILED
workdir/.gap-closed-preliminary.tan.data: FAILED
workdir/.reads.bps: OK
workdir/.reads.idx: OK
workdir/assembly-test.assembly-test.las: OK
workdir/assembly-test.dam: OK
workdir/assembly-test.reads.las: OK
workdir/gap-closed-preliminary.dam: FAILED
workdir/gap-closed-preliminary.fasta: FAILED
workdir/gap-closed-preliminary.gap-closed-preliminary.las: FAILED
workdir/gap-closed-preliminary.reads.las: FAILED
workdir/reads.db: OK
md5sum: WARNING: 15 computed checksums did NOT match
```
any advice on how to get the example dataset running would be greatly appreciated,
Thanks,
Rishi