Looks like i found the answer myself.
It turns out that there is workspace limitations in opera. And my workspaces were not merged because the first PC has already 5 workspaces ... Oh what a ridiculous limit ?! Looking forward to 73 version release where this limit will be increased.
When i turned off workspaces in PC-2 i got all my tabs back(but now unsorted in previously created workspaces).
Once again, very weird and confusing limit ...