Transponders are rarely run at maximum power levels. The uplinker creates a link budget that sets the power level and bandwidth based on the programming content, resolution, picture quality, downlink reflector size, efficiency, feed performance, weather conditions, uptime and priority requirements. The uplinker may use the carrier to carry up to the full contracted bandwidth and power levels. The uplinker is responsible for monitoring and compliance. The satellite owner monitors for compliance and notifies if the parameters are not within specification or link budget.
The strength of the analog carrier power can remain at the same link budget level no matter how many services or pids are in the digital transport stream. Dropping a service from the digital transport stream doesn't make the remaining services more powerful.
Receiving a transponder at one time and not another could be that the uplinker increases the transmitter power to overcome attenuation by cloud cover or local storms. Could be that the atmosphere is not attenuating the signal in your region due to lower moisture or temperature.
With a mini BUD, a 1/2dB increase or decrease makes the difference between receiving or not. With commercial down links, they have a 10,15,20dB headroom and a 1/2dB variation is not even noticeable.