can't upload images: bug with 2.11.6?

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I've a working isotope 1.3.6 stable 6 with contao 2.11.5
I can't upgrade isotope, if I do all hangs
but I've updated contao to 2.11.6 and now isotope doesn't upload product images any more

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I've copied site in localhost and upgraded to isotope 1.3.8 stable 6, same problem
later I'll try to update to 1.4 beta

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I downgraded Contao to 2.11.4 and now it works