I bought 6pc shelly 1L, on all same issue. When you hit case hard, relay is unstack, so i suppose hw issue with cheap chinese relay. I created a ticket as I bought directly.
shelly 1L use white small chinese relay rated 4A, shelly 1PM which works ok use bigger one black rated 16A. using inrush CL is not an option for me, even not specified in product specs.