Loss of connection on PfSense: help with traffic shaping

We are an organization based in Central Africa with 4 independent internet connections: one VSAT, two 3G mobile phone networks and one ADSL. We give access to 60-65 users. A smart switch regroups the 4 independent network by asymmetric VLAN configuration and pass them over to VLAN supported access points with 4 SSIDs for the 4 independent networks. We are experiencing short but frequent loss of connection for all of these links. This is most pronounced and disrupting for the VSAT connection, which uses PfSense 2.3 as firewall. We suspect that network congestion, based on large network buffers, high latency, low bandwidth (typically around 1 Mb/s or less on the VSAT connection for the download link during the day) and high usage is a reason for the loss. Misconfiguration of asymmetric VLAN on the D-link web smart switch that goes to the access points might also be a possibility. We are looking for someone to help us pinpoint the problem. As the solution will likely involve active queue management and traffic shaping in PfSense, we are looking for someone with experience in this domain. The configuration should involve prioritization of applications that need remote access to sites based on their IP address.