Trying to work out if my employer is dodgy and hasn't been paying my NI

[NIproblem]

I'm on hold to HMRC, but got to pick up my DC from nursery in an hour, so not sure I'll get through to someone by then!

I have 2 employers as I work PAYE PT for both - set hours per week.

Employer A - I get a monthly payslip with a full breakdown of all my deductions that month, then a summery to date. This includes PAYE/Employer NI & Pension. It also does the same for my employers eg their payments for NI & my pension. Employer uses a payroll company who then pay me on a set date every month.

Employer B - Monthly wage slip (if I am given one!) includes my deductions, eg Employer NI & Pension. This is the employer I think might be dodgy as its a small company, boss is shady, and there are many dodgy practices going on, Boss uses a really cheap payroll company and manually pays me, and other employees, every month (even though my is the same every month and I've been there years) payment generally is paid on the right day, even if it is 10 mins to midnight, but is occasionally late if my boss is unwell or on holiday and forgets!

Using Tax Year 2023-2024 as an example:

My NI record on the HMRC portal shows contributions of £3,847.86

Employer A - last payslip before end of tax year shows Employee NI deducted £3827.72 total for the year, so does my P60.
Employer B - last payslip before end of tax year shows Employee NI deducted £316.36 yearly total, but my P60 shows £20.14 NI deducted for the year.

If I add up the P60's, that makes sense, but what doesn't make sense is why I've had £316.36 deducted from my wages by Employer B when only £20.14 shows on my P60 & NI record?

Am I missing something obvious?

HMRC only give a single figure on their portal, so I haven't got a list of where the NI contributions have come from.
Luckily both employers do pay into my pension as their portal is very clear about where the payments have come from so I can track those.

It sounds like employer B’s payroll provider may have messed up.

Get all your payslips for the tax year and send copies + copy P60 to boss, with a list of the ‘ee NI deductions and ask Boss to send question to payroll company why the P60 total is different to the sum of the payslips. It’s unlikely boss is reconciling at that level, but payroll company should be able to

Unfortunately I have left the dodgy company and the boss would not answer my emails, last time I asked and did get an answer I was told the payroll company is bust and so that's the end of it.

I did manage to get through to HMRC after 55mins on hold.
Was told I need to write in to HMRC with my query & the evidence I have and they will investigate.
They were helpful, it sounds likely my employer stole from me or defrauded (stole) from HMRC as all the accountancy 'mistakes' over the years are in the employers favour. There are other employees at this company and if HMRC found that my wages have been falsified, then they check the whole lot.

It's not huge sums every month, but over the 20 years or so the company has been operating and the number of wage slips over those months/years then it's a really significant sum. Obviously the boss thought the scam would be worth it because her employees wouldn't think to check as I had assumed a using a payroll company meant everything was checked.