VM 2.0.20b Joomla 2.5.11 PDF invoice logo cropped

[lorartemis]

Hi, I've upgraded a client site from virtuemart 2.0.18a to 2.0.20b which is working fine, except for the layout of the pdf invoices.    The logo is cropped for some reason, should it be using the smaller version of the file, the thumbnail?   If so, what do I change to correct this?
The server is running php 5.3.25 and all of the joomla requirements are met.    the pdf itself creates and downloads very quickly, which is great.   

Thanks for any advice.     I've attached a quick screenshot of the logo which is almost cut in half.   I'm happy for it to be smaller on here and it works fine on the printed version of the invoice.    I'm not using any overrides and the issue occurs with both my artisteer template and Beez.     

Edited to expand on php version for clarity.




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