diff --git a/.github/tests/mix-assert.yaml b/.github/tests/mix-assert.yaml
index d1be13155..84fe05660 100644
--- a/.github/tests/mix-assert.yaml
+++ b/.github/tests/mix-assert.yaml
@@ -9,7 +9,7 @@ participants:
     cl_type: lighthouse
   - el_type: reth
     cl_type: lodestar
-  - el_type: nimbus
+  - el_type: geth # temp remove nimbus-eth1 till they fix their bugs
     cl_type: grandine
 additional_services:
   - assertoor
diff --git a/.github/tests/mix-with-tools.yaml b/.github/tests/mix-with-tools.yaml
index 82a740da8..4a1120dc5 100644
--- a/.github/tests/mix-with-tools.yaml
+++ b/.github/tests/mix-with-tools.yaml
@@ -3,6 +3,7 @@ participants:
     cl_type: teku
   - el_type: nethermind
     cl_type: prysm
+    cl_image: ethpandaops/prysm-beacon-chain:webfix
   - el_type: erigon
     cl_type: nimbus
   - el_type: besu
diff --git a/src/package_io/input_parser.star b/src/package_io/input_parser.star
index e8972c5c0..847d23ea5 100644
--- a/src/package_io/input_parser.star
+++ b/src/package_io/input_parser.star
@@ -378,7 +378,7 @@ def input_parser(plan, input_args):
 
 
 def parse_network_params(plan, input_args):
-    result = default_input_args()
+    result = default_input_args(input_args)
     if input_args.get("network_params", {}).get("preset") == "minimal":
         result["network_params"] = default_minimal_network_params()
 
@@ -397,8 +397,6 @@ def parse_network_params(plan, input_args):
         if "vc" in input_args["participants_matrix"]:
             vc_matrix = input_args["participants_matrix"]["vc"]
 
-        participants = []
-
         for el in el_matrix:
             for cl in cl_matrix:
                 participant = {k: v for k, v in el.items()}
@@ -708,9 +706,13 @@ def get_client_node_selectors(participant_node_selectors, global_node_selectors)
     return node_selectors
 
 
-def default_input_args():
+def default_input_args(input_args):
     network_params = default_network_params()
-    participants = []
+    if "participants_matrix" not in input_args:
+        participants = [default_participant()]
+    else:
+        participants = []
+
     participants_matrix = []
     return {
         "participants": participants,