Rising/Falling Edge Detection for interrupt generation circuit issues
The problem is that when the reed switch opens, the GPIO2 pin is pulled down through the 10 meg resistor. The parasitic caps around your circuit might produce an erratic and unpredictable behavior, because the node GPIO2 is basically high impedance.

To solve your problem, the easiest way I see is to reduce the 10 M as low as your reed switch allows, change RD to at least 10x RPD, or 100x if possible, and reduce C accordingly to keep your time constant.

You can also try to build up a push pull driver for your edge detection circuit, but things get a little more complicated.

I will close with another suggestion: I assume you have a microcontroller that reads these pulses and does something as a consequence. Most (all?) microcontrollers allow you to edge trigger an interrupt, so basically they already have inside all the necessary circuitry. Read your micro's manual carefully, I bet your solution is just changing a bit in a register somewhere.