One of possible causes might be Extended Events. You can upgrade to 11.6.2 version of Spotlight where we have improved performance of monitoring using extended events.
This change in 11.6.2 reduces network I/O and ultimately disk I/O on the monitored instance and will also sample more events.
In earlier version of SQL Server (2008 and before) Extended Events were not as good as in the later versions. It could also depend on the installed hotfixes etc, or the overall infrastructure (cores + network interface) etc.
Alternatively you can disable Extended events only on connections causing the problem (you can disable from the properties of a connection - there should be a checkbox in versions 11.6.1 and later)
