bad IP traffic

My company NIDS - i.e. snort 2.0 - is triggering since three/four days a lot of "BAD-TRAFFIC bad frag bits" alerts.
These come out when a TCP packet has both fragment and don't_fragment bit on.

Target of these alerts is almost always the IP address of a particular Web Server (one of our server farm).
Other alerts are triggered on this target, some are common ones such as Apache worm for Apache old version but this is a usual maltraffic, but other ones are of type "bad TCP/IP traffic", such as anomalous TTL values for packets.

It seems to me this could be a scan/gathering info technique, is it correct? can this be a False Positive ? Can this
be something more dangerous?

Any help will be very appreciated,

Cheers,

Max

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