error in two-way lighting

[witsend]

Could someone please help me sort out the wiring where I have had to replace a pushon/pushoff module in a two-gang switch which is one of two switches that controls a light fitting.

Each module is of the type with 3 connections alongside each other at one end of the block - L1, L2, COM .

The other [unaffected] switch in the other room has 3 wires each wired separately into the module - L1: red, L2:blue, COM: yellow. I checked and they are securely tightened.

The switch where I changed the module has wiring:

Hole 1/L1: 2 reds
Hole 2/L2: 2 wires - one Blue and one black with red live sleeve notification
Hole 3/COM: 1 wire - one yellow with red live sleeve notification

I thought I had copied down the arrangements but appear to have made an error. I can set the two switches so that the light fitting can be switched off and on from the same end at both switches. However if I turn one of the switches off, I cannot switch on at the other end i.e. no 2-way function.

The modules and screw fittings are so flimsy these days and screws struggle when two wires have to be wired into one hole but I beleive they are now securely in place. I mention this in case short circuit within a module is one possibility.

I have multimeter but would need instruction on how to run checks.

Can anyone suggest different wiring that will re-establish two-way

Thanks

[witsend]

Just resolved my own problem. Wiring plan was OK but the components inside the module make poor connections. 3 metal lips come off the small PCB and are pressed into contact when the screws push into the fittings which hold 1 - 2 wires. If these are only slightly loose, sparks occur. Poor design and manufacturing quality in the attempt to miniaturise and cut costs.

[ElectekAir]

try to switch the L1 and L2 connections ( most sparks dont get it right first time too)
only on one of the switches though