I don't recognise that, but for some reason I'm thinking Chinese.
I will guess that the MCBs turned "off" with no identifying label above may be unused.
If this brand makes RCBOs to fit, you could have your electrician fit one or more on the non-RCD side, and move the most suspect circuit(s) onto them.
What this will do, is give that circuit its own independent RCD; so that
1) if it does have a fault, and trip, then you will not lose any other circuits* which will be more convenient
2) if the tripping is due to the accumulation of small leakages from several circuits, the separated one will no longer be adding to that accumulation, and may prevent the main RCD from tripping
p.s. if the washing machine is under suspicion, buy a 13A RCD plug-in adaptor (as used with lawnmowers) and plug in the washing machine through that.
p.p.s you might also ask your electrician to fit some Blanks in the unused MCB-ways.
*probably
I will guess that the MCBs turned "off" with no identifying label above may be unused.
If this brand makes RCBOs to fit, you could have your electrician fit one or more on the non-RCD side, and move the most suspect circuit(s) onto them.
What this will do, is give that circuit its own independent RCD; so that
1) if it does have a fault, and trip, then you will not lose any other circuits* which will be more convenient
2) if the tripping is due to the accumulation of small leakages from several circuits, the separated one will no longer be adding to that accumulation, and may prevent the main RCD from tripping
p.s. if the washing machine is under suspicion, buy a 13A RCD plug-in adaptor (as used with lawnmowers) and plug in the washing machine through that.
p.p.s you might also ask your electrician to fit some Blanks in the unused MCB-ways.
*probably