Model: 3-mo. old BCPP

Symptom: Normal takeoff & hover characteristics 1st 30 seconds of flight, whereafter head speed drops over the next 45 seconds or so to point where BCPP will only hover weakly a foot off the ground.

Detail:

1. Installed G90 which came right up no problem & performed well. After 10 minutes or so of marvelously stable hover & slow flight I did an unintentional backward sliding landing i.e. it was sliding on the stock skids (guess I was a little too distracted by the G90's nice performance!), which would have been of little consequence except it grazed a metal garage door & destroyed the woodies. Also a few consecutive teeth on main gear looked ragged.

2. Replaced main gear/shaft (nothing I haven't done before).

3. Balanced, installed & tracked replacement woodie syms (again, nothing I haven't done before). Topped off the stock Li-Po while repairs were underway.

4. Fired up & lifted off normally.

5. After about the 1st 30 seconds of flight, the motor/head speed started reducing despite throttle advance @ Tx. Within the next 30-45 seconds head speed was so slow as to prevent lift more than a foot off the ground.

6. Replaced main stock motor with a spare new stock motor (I had already replaced the tail motor 2 weeks earlier as part of gen'l PM). Topped off stock Li-Po.

7. Fired up, same symptom.

8. Disconnected G90, reconnected stock gyro. Topped off stock Li-Po.

9. Fired up, same symptom.

10. Re-confirmed the symptom with my alternate stock Li-Po (about 3 weks old).

Doesn't seem like a radio problem, so:

Possible Cause(s)?:

A. A failing ESC in the stock 3-in-1.

B. Less likely, failing main shaft bearings.

C. Even less likely, my stock charger, despite its outwardly normal behavior, is no longer charging the Li-Po's to capacity even though it says it is.

Have scoured this forum for a few weeks & don't recall seeing this addressed.

I'm a long way from going brushless, Spektrum, etc. & don't really want to upgrade (yet) anything more than the G90.

Q1: Any of you BCP/P operators experienced anything similar &, if so, how did you resolve?
Q2: If A., above, is this my chance to replace the 3-in-1 w/a standalone ESC?

BTW, I've derived more downright-obsessive enjoyment from this flying machine than I can pen. I'm committed to its care and feeding and w-i-l-l see it develop to its highest potential. Uh oh, am I a father again?

Thank you in advance for reading this long post.