@javeedf  I was able to replicate this and get it working with the following. Possible the top where clause is not filtering as you expect. 

Try 

`where matches(toLowerCase(device.name), toLowerCase(host_pattern))`

get_vrrp_details(host_pattern: String) =
  foreach device in network.devices
  where matches(toLowerCase(device.name), toLowerCase(host_pattern))
  foreach interface in device.interfaces
  where isPresent(interface.routedVlan)
  let routedVlan = interface.routedVlan
  let ipv4 = routedVlan.ipv4
  let fhrp = ipv4.fhrp
  let vrrp = fhrp.vrrp
  where length(fhrp.vrrp.fhrpGroups) > 0 || length(fhrp.hsrp.fhrpGroups) > 0
  select {
    deviceName: device.name,
    interfaceName: interface.name,
    vlan: routedVlan.vlan,
    fhrp,
    vrrp,
    hsrpFhrpGroupsCount: length(fhrp.hsrp.fhrpGroups),
    vrrpFhrpGroupsCount: length(fhrp.vrrp.fhrpGroups)
  };

thank you for your response,

This issue is seen specifically on Dell OS10. have you tried with Dell OS10?

sorry I missed to mention in my question

@javeedf That may be a different issue, can you please open a support case?