Dual coil or single coil controlled? (may need several flyback diodes). Wouldn't mind seeing your control circuit, code and part# for the relay. I'm quite familiar with latching type relays.
Incandescent lamps have the highest derating factor for relays. Definitely its inductive component is very high.
From here ...
and here ...
Snubber circuits by design would pass a small current ... enough to make CFLs flicker. Not sure about LED bulbs, but adding a snubber would probably make them impossible to turn off
That does not sound right, unless i am not understanding you correctly.
Incandescents are resistive, not inductive, however their resistance swings roughly 10 to 1. So during startup they might draw 10 times the normal current.
An inductive load would do just the opposite: draw less current during start and more later. The inductive kick back is usually a problem however when the device is switched off.
The relay 'welded' contacts can come from a high start up current or perhaps arcing during turn off. To resolve the problem it has to be determined which is causing the problem, or possibly both.
A snubber would be the idea if the relay contacts arc over during turn off.
If the problem is high startup current though then some kind of current limiter would be needed.
A typical snubber for DC would be a diode, bleeder resistor, and capacitor. The capacitor absorbs energy when the contacts open, and the energy slowly dissipates in the resistor. The cap and resistor and diode have to be sized according to the amount of kick back energy it has to handle and how frequently the switching action occurs. A snubber for AC could be similar, but instead of a diode a bridge rectifier. The rectifier allows energy to flow only into the cap, and the resistor bleeds the energy off at a given rate. If the contacts switch fast then the values have to be sized to handle the energy at the rate needed. Some efficiency is lost because of the bleeder resistor and it conducts when the relay contacts are open so the sizing is a tradeoff between fast action and low power dissipation. Perhaps a TVS instead.
If the problem is more about a high start up current, then some sort of current limiting is needed if the relay contacts can not be oversized. Of course going to a heavy duty relay would be a good idea because current limiting isnt that easy. For example, a second relay to keep a resistance in the circuit for a short time and then switch the resistance out by shorting it out and thus allowing full current. An inductor would work here too, but sizing and secondary behaviors are not that easy to deal with.
Another idea is an inrush thermistor. These are made for the very purpose of limiting current during startup of various devices like motors and capacitor filters. They are available in a variety of sizes, but they do get hot during normal operation, so that has to be dealt with.
So really the first thing to do is find out if it is an inrush current problem or an arc over problem, or both.