Apache httpd mod_cache_socache Denial of Service Attacks

Dear All,

I have a problem with my sophos xg 125, i have enabled the IPS and i found in the sophos dashboard in the network attacks field, i found daily attacks

(5000 hits/day) from the Apache httpd mod_cache_socache Denial of Service with SID: 1180327051

i block it and i have checked from the log viewer and it is denied now

the issue is after i denied the rule above, 50% of the websites i visit is taking long time to load in addition to some pages doesn't open at all,

if i allow the denial of service  attack above again, all pages load normally.

should i allow it or should i block it and how to fix the slow loading too

thanks,

khaled.