Problem with firewall-accelaration and ping

Do you have migrated SD-WAN Rules or is this a fresh installation? 

It's not a fresh install but I don't have any sd-wan rules. In practice this firewall was in a different location, now I took it to the main office and I wanted to replace the current pfsense with the xg. I cleaned it from all the rules and redone the configuration from scratch but I come across these strange errors, from some computers I can ping outwards without problems while from other computers only the first packet comes out then the others all expire .
If I disable firewall-accelerated then the problems are over.
Previously the version was 17, but I had already migrated to 18 and everything worked in the previous location.
I do not understand why...

It's not a fresh install but I don't have any sd-wan rules. In practice this firewall was in a different location, now I took it to the main office and I wanted to replace the current pfsense with the xg. I cleaned it from all the rules and redone the configuration from scratch but I come across these strange errors, from some computers I can ping outwards without problems while from other computers only the first packet comes out then the others all expire .
If I disable firewall-accelerated then the problems are over.
Previously the version was 17, but I had already migrated to 18 and everything worked in the previous location.
I do not understand why...

Can you reimage this appliance with a V18 image? 

https://support.sophos.com/support/s/article/KB-000036812?language=en_US

Only if you have time for this and the new configuration is not that big.

Because i can think, there is an problem with the config migration and something is wrong with the fastpath technology on this appliance. 

it could be a good idea, this is a virtual appliance and I'm afraid that doing the re-image will change my serial and then my NFR license will no longer work.

You can reuse your SN as often as you like but not at the same time - So if you reimage your appliance, delete the old at this time, it will not be any issue to reuse your SN. 

Just be careful by power down the old appliance and power up this later. 

XG will generate on registration a token and device ID, which will be booked on Sophos licensing servers. Only the new appliance can communicate to our backend server. The old will be removed and cannot communicate anymore. 

Perfect, thank you!

as soon as I can I make the new image.