Set heart beat timeout explicitly for these virtual couplers.

coupler/opc-ua-server/coupler1.sh

 #!/bin/bash
-./server -m 1 -b 1 -i 1 -l 2,3 -t 100
+./server -m 1 -b 1 -i 1 -l 2,3 -t 100 -o 1000

coupler/opc-ua-server/coupler2.sh

 #!/bin/bash
-./server -p 4841 -m 1 -b 1 -i 2 -l 1,3 -t 100
+./server -p 4841 -m 1 -b 1 -i 2 -l 1,3 -t 100 -o 1000

coupler/opc-ua-server/coupler3.sh

 #!/bin/bash
-./server -p 4842 -m 1 -b 1 -i 3 -l 1,2 -t 100
+./server -p 4842 -m 1 -b 1 -i 3 -l 1,2 -t 100 -o 1000