WORKING PERMIT DELAY

Hello,

I have landed up in a strange issue.

My new recruiter is a consultancy  IT company who would do my WP process and salary payouts.
Now apparently, after 2 months of putting down my resignation with my current company, I came to know that they haven't started my WP process due to some misunderstandings within their company.

They are saying they will start today and send me the evidence receipt from the brussels government that all the documents that are required for the WP are filed and are correct.
With this receipt and evidence, I am still eligible to work for the client till I get the physical copy of the WP.

What they say is it valid ?  As per my understanding, unless I have the WP, I cannot start working in Belgium.

Should I still go ahead with this company or look out for some other offers ?  Because though I already have a signed contract from the consultancy, what if there is a major delay in Working permit ? I may loose my current job and also not have surety of working with this new company

Or should I wait patiently till I get the evidence that WP has been filed and that implies that I will surely get the WP with some delay.

Please do help me out with your advice. Many thanks in advance.