Instable: Misses about 50% of the orders

Hello

Hope you can help.

About 50% of all orders are not passed to google analytics convertions e-commerce.
These orders do not shown up at all.

It does not matter what payment gateway will be used, it happens everywhere.
Very instable.

I tried anything of the settings, but none of them changed the behavior.
Turned off the cache of the “order_received” page, too.

Do you have any idea what causes this problem?

Any help very appreciated.

Thanks Armin

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