You should be VERY Gratefull that they tripped as this means that Your Life was saved
Those 30mA is the Maximum Fault Current that is allowed to run through Your Heart as more is Very likely to Kill You !!!!!
Time to either Throw-Out that old welder or having a Qualified Tech repairing it ...!!!
As a new very good Multi-Welder can bebought for around €200 (today with the Current British state of affair) ~ £200 .... I doubt that keeping the old (unless simple repair) is justifiable ....
Clarification - those new (2022) Multi-Welders are extremely good @ welding Steel, Stainless-Steel. + They can weld other materials and even Aluminium (although Alu-Welds look horrible + lot of spatter).
They are called Multi-Welders as they can do Stick, MIG, MAG and TIG.
Per