Don’t ignore it, you will eventually discover the reason.
Don’t rewire, bypassing the rcd. The fault finding will be difficult due to its intermittent nature.
I am.sure you have mentioned in previous posts what kind of boiler it is but I can’t remember. Is it a gas or oil boiler?

JohnnyD, one or more RCDs? The standard ID (Interrupteur Différentiel) trips around 23 mA. Too difficult to produce these electro/mechanical devices with such a precision that they trip at exactly 30 mA within +/- 0.1%. A lower value to be on the safe side, otherwise they would probably have to throw away 25 % of the production, many tripping above 30 mA, gaussian curve etc.

Fault currents to earth are cumulative. The old desktop computers with their power supplies produce each a leakage current of 2 to 4 mA. Throw 10 workstations together, a laserprinter and you almost reach the max current of a 30 mA RCD. Sometimes RCDs are too sensitive, already tripping below this nominal trip current. Replace a RCD if trip current is more than 30 mA or lower than 15 mA. Or trips too slow.

Question: anything else with a possible leakage current (electric kettle?) connected to the same circuit as the boiler and under protection of the same RCD? Condensation issues somewhere?

Divide and rule can help, more RCDs in your installation électrique.

The burner is this one, new things that have been added recently are an electric towel radiator in the bathroom, and a kettle

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@ JohnnyD,

1/ Kettle + electric towel radiator added: comes at a price: more tiny fault currents to earth.

2/ Divide and rule: please more than one RCD, see diagram in this document.

3/ Divide and rule continued: boiler connected as a circuit specialisé, with its own ID or disjoncteur différentiel? Or sharing the same RCD with others, your kettle and electric towel radiator?

4/ Divide and rule part III, the circuits specialisés in France.

5/ Department DIY: the ID as a possible trigger happy suspect. Useful is this tester VT35 from Multimetrix: checking sockets for phase and neutral position and the presence of earthing. Also the possibility to test RCDs with different leakage currents to see if and at what fault current it does its job. Complicating factor in practice: the presence of small leakage currents to earth from other connected equipment adds up. Switch off everything, unplug every appliance. Use a socket close to the  consumer box. With this little tester you don't know within how many milliseconds the interrupteur différentiel will react. But then again, this instrument costs less than 30 euros, professional meters start at 500 €.

6/ @ PE, filtre antiparasite, better known as an EMI filter. The usual arrangement of only a handful of passive components, to suppress noise, incoming or outgoing. Also adding to the 'background' noise of cumulative fault currents to earth.

If you do not know what your doing get an expert that's what I do 😃

JD, from a fully authorized source this information about the effects of cumulative leakage currents. A lot of words and expensive measurement equipment to expalin something every electrician, DIY or professional, already has in his or her intellectual baggage.

I remember doing a rewire on a place here, done the kitchen general purpose socket outlets and all tested ok, few days later after the chippy had finished putting the kitchen in I was back there finishing off, though nice cup of coffee, plugged the kettle in, POP, thought that's knackered and slung it in the bin, then the customer rings me when she puts the microwave in again POP, same socket, took it down, the chippy had taken the sockets off to fit his upstand at the back of the worktop, and had put the cables back wrongly so kettle and micro were trying to work live earth, dustman had been and gone with kettle by then.