Jaco-S

Hi everyone We recently bought a house that has all gas geysers / water heaters and there is an inconsistency with the hot water flow. 𝗧𝗵𝗲 𝘀𝘆𝘀𝘁𝗲𝗺 Medium size gas heater, set to 65 degree celcius two x 19kg gas bottels: Switching between the two as the pressure decreases. Copper pipes to the showers, baths and basins. Mixer taps 𝗧𝗵𝗲 𝗽𝗿𝗼𝗯𝗹𝗲𝗺 I will open the mixer taps until there is hot water, then slightly adjust the tap to the desired water temperature. Thereafter, the water will get very hot as if the cold water stops flowing. It will be like this for about two minutes then return to the initial mixed temperature. After about 5 minutes, the water will become cold and this lasts about another 3 - 5 minutes. I will close the tap completely, then open it again and only thereafter the hot water returns but only to start the entire cycle again. This happens every time regardless if I replace the gas bottles, replace the batteries or adjust the temperature on the geyser. I need to add, I have zero experience with these types of systems. Can any of you gas-system-brainiacs steer me in the right direction?