New Water Heater - Pilot keeps going out - costing me $$$

[David Hald]

In February 2021 I replaced both water heaters in my duplex, since tenants frequently complained about no hot water and the units were old anyway. 

Expecting this to solve the problem, I was surprised when the same repair call came back again. I told the PM to send the same installer of the water heaters out to fix his work, which they did. 

To no avail, this problem keeps recurring, and, needless, to say is eating into cash flow in an already high-maintenance cost property. 

The water heaters are in the flagstone basement of a 1900 midwest duplex. Any recommendations on how to keep the pilot lights consistently lit ?