Problem working with the P9242 and P9221

Hello,

We are developing a product which consists of P9242 and P9221. Main related components and the structure is shown in the following image. 
Our device has three main use cases,
1. Charge the battery with P9221 Receiver using wall connected P9242 transmitter (A)
2. Use the P9242 transmitter (B) to charge a phone with the battery power
3. Use the P9242 transmitter (B) to charge a phone while receiving power from P9221 Receiver using P9242 transmitter (A)
Above use cases 1 and 2 work perfectly, but we are having a problem with use case 3. 
When we try to use P9242 transmitter (B) while receiving power, P9242 transmitter (A) and P9221 receiver stop working and start again. This happens periodically around five times within a minute (it varies, sometimes it works for a while and go off). When this happens both lights of the P9221 receiver and P9242 transmitter (A) turn off and start again after around around 2 seconds. We measured all the current and voltages using an oscilloscope in each power path and could not see any transients. P9221 receiver output current is around 1000mA and not exceeding the ILIM nor any transients as we could see with the oscilloscope. Voltages of the TS pin and VRECT are in the preferred range and no faults light indicators are visible from the P9242 (A) when this happens.
Here I will attach some oscilloscope current and voltage readings from the P9221 receiver output. 
Current output from the P9221 (measured through series resistor 0.25Ohms) max is around 0.95A (ILIM is 1.25A). Current drop happens when the above stated incident happens. 1st image is focused when drop happens. 2nd image shows current drops within around 20 seconds. 3rd image shows both the voltage(Blue CH2) and the current.
To recreate this error we can just connect the P9221 receiver to the P9242 transmitter as shown in the image. When we try to charge a phone while receiving the power this error happens. 

 Appendix
  1. We used iPhone X, iPhone XR, Samsung Galaxy S9 and S20. We can see the error with all these phones
  2. BMU is CHGIN current is limited to 1A (programmable). So it is not asking for more than 1A from P9221. We even reduced the value to 800mA. Problem persists
  3. We changed the power supply of the P9242 as well with 12V 3A. But same problem happens 
  4. We used development kits for these experiments
  5. The components we used
    1. BMU - MAX77818
    2. 12V up converter - TPS61178
Thank you 
Isuru Kalhara
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