Beckett Burner Woes Or Something Else?

HTM

We hope to make it through one last heating season with current late 1980's W M boiler. Likely replace with Buderus
unit which your experts assisted with on sizing/piping questions. System is zoned hot water baseboard and c.i. radiator plus indirect h.w. tank. Last evening before the start of the Eagles game (we are outside of Philly), noticed the boiler would run 3-4 minutes and then shut down. Between long intervals it would restart, run for a few minutes and then stop.
Burner has a Honeywell R7284 controller. At beginning of ignition, displays ohms just over 300. There is a slow but steady drop-off to high 230's/low 240's, then the burner cuts out. Around 250 ohms, the main B&G flow valve (looks to be 1-1/2") in the black pipe manifold above the boiler starts clattering loudly. Frequency increases as the ohms drop.
Is an electrical issue causing the burner motor to shut down?
Is the clattering valve a sign of the boiler getting ready to shut off or is this a malfunctioning valve that is somehow causing the boiler/burner to stop?
Thanks in advance for all comments/suggestions.

DZoro

what was your water temp. and pressure during that time?

HVACNUT

Sounds like it's going into recycle after flame loss or ohms out of range. Time to get the burner serviced.

STEVEusaPA

High ohms would cause the control to lock out. But along the lines of @Dennis thinking, sounds more like the boiler is running up to temp and shutting off. Bad circ, bad control, air in system, etc.