collapse_isoforms_by_sam.py out of memory

[SY348]

Hello，
When I run collapse_isoforms_by_sam.py with a big .sam file (~90GB), it ran quite slowly and always ended with an error 'OUT_OF_ME+ 0:125'. Are there any way I can optimize the project?
The codes're as follows:

python collapse_isoforms_by_sam.py --input isoseq_flnc.Transcript.fastq --fq -s isoseq_flnc.Transcript.sorted.sam -o TEST

Besides, I've read the example data, and I don't understand why PB4.2 contains two isoforms without containing PB4.3 as all these three belong to the same genomic region? The same problems for 1.1, 1.2 and 1.3. How the project define if the two reads belong to a same loci.index?

Thanks!