10+ students received anomalously low marks in one module despite strong performance elsewhere: is a collective appeal worth pursuing

Hi everyone,
I'm in my final year of a Law degree and would really appreciate some advice.
I recently received a 55% in a Medical Law essay which genuinely shocked me. I am averaging upper 2:1 /1st across all my other modules and have never scored below 60% except once in second year when I was unwell. But I accepted the results because there’s not much I can do.

The following day a classmate mentioned she had spoken to others who received 54%, 55% and 56%. We now have a group of 10+ students with the same concern. These are not struggling students BTW, they are constantly achieving 2:1s and firsts across their other modules. One student who consistently scores 70%+ received a 55%. Another received a 49%.

Some context that we feel is relevant:

1. multiple industrial strike disrupted teaching throughout the module.
   2.She’s a sole marker, The lecturer confirmed in our final lecture that she is the only person marking the entire cohort with no second marker.
2. In that same final lecture she explicitly advised us not to waffle, avoid introductions and get straight to the point. Several of us independently adapted our writing style based on this guidance. We then received feedback citing superficial discussion, basically directly contradicting the instructions we followed.
   4.The disparity between our medical law marks and our performance across comparable modules is difficult to attribute to individual student performance given how many of us are affected.
   We are considering a collective appeal but understand it must be evidence based and factual rather than simply expressing dissatisfaction with our marks.
   My questions are:
   Has anyone successfully pursued a collective academic appeal in similar circumstances?
   Is the contradiction between assessment guidance and marking feedback a strong enough ground?
   Would the absence of second marking strengthen our case?

Any advice would be appreciated. Thank you in advance.