With 16F876's, both CCP modules use the same Timer in PWM mode (TMR2).
If you change the frequency of one, the other one changes too.

With a 4 Mhz crystal, the minimum HPWM frequency is 245 Hz.
Since you are using a 1 Mhz crystal, you can get down to 62 Hz, but you have to specify the frequency as if it were running at 4 Mhz.

If you want 100 Hz, then specify 400 Hz in the HPWM10 command.
93 is way below the minimum.
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