Suddenly invalid values

[cagcoach]

In our shop we suddenly get the error messages

...
Invalid value at 'body.entries[3762].product.adult' (TYPE_BOOL), "Nein"
Invalid value at 'body.entries[3762].product.identifier_exists' (TYPE_BOOL), "Ja"
Invalid value at 'body.entries[3763].product.adult' (TYPE_BOOL), "Nein"
Invalid value at 'body.entries[3763].product.identifier_exists' (TYPE_BOOL), "Nein"
Invalid value at 'body.entries[3764].product.adult' (TYPE_BOOL), "Nein"
Invalid value at 'body.entries[3764].product.identifier_exists' (TYPE_BOOL), "Nein"
Invalid value at 'body.entries[3765].product.adult' (TYPE_BOOL), "Nein"
Invalid value at 'body.entries[3765].product.identifier_exists' (TYPE_BOOL), "Nein"
Invalid value at 'body.entries[3773].product.adult' (TYPE_BOOL), "Nein"
Invalid value at 'body.entries[3773].product.identifier_exists' (TYPE_BOOL), "Nein"
Invalid value at 'body.entries[3778].product.adult' (TYPE_BOOL), "Nein"
Invalid value at 'body.entries[3778].product.identifier_exists' (TYPE_BOOL), "Nein"
Invalid value at 'body.entries[3779].product.adult' (TYPE_BOOL), "Ja"
Invalid value at 'body.entries[3779].product.identifier_exists' (TYPE_BOOL), "Ja"
Invalid value at 'body.entries[3780].product.adult' (TYPE_BOOL), "Nein"
Invalid value at 'body.entries[3780].product.identifier_exists' (TYPE_BOOL), "Ja"
...

for any product we try to submit. Does someone know this issue?

greedings
Christian