If the DVD Drive makes "grinding" or "scrubbing" noises and fails during read, write or finalizing operations the disc is slipping on the rubber hub. Cleaning the DVD Drive rubber hub is the usual corrective for these problems.
The U88 error comes when there are other reading problem(s) with a disc in the machine. There might be any number of causes for these errors, a dirty or failed lens/laser assembly, a disturbance to one or more of the ribbon cables from the DVD Drive to the Digital PCB, or a problem with the Digital PCB itself. The U88 error may be accompanied with "clunking" or "chugging" noises as the DVD Drive attempts to read the disc. You mentioned "cleaning." Did that a cleaning include the DVD Drive lens? A gentle lens cleaning might restore functionality.
The U61 error is similar to the U88 error but occurs when there is no disc in the machine. The cause for these errors may be the same as for the U88 error.
Rubber hub and lens cleaning is addressed in this thread:
If the lens/laser assembly has failed or there is a problem with the Digital PCB then the Panasonic-approved procedure in 2006 models like your DMR-ES46V is replacement of the DVD Drive and the Digital PCB together as a "module." That module is described as the RFKNES46VP RAM/DIGITAL PCB MODULE, $621.69 for the parts alone through a local repair shop.
Panasonic offers a $130 flat-rate repair through their corporate Panasonic Digital Service Center in Elk Grove Village Illinois. That $130 flat-rate includes all the parts and labor (and return shipping) necessary to return a Panasonic to new functional condition. See this post:
One must decide if it is cost effective to repair or replace the DMR-ES46V. (I have a DMR-ES46V that is "dead." I have considered the $130 flat-rate repair for this outstanding product. I currently have other Panasonics that are serving me well so the DMR-ES46V may not be repaired.)
If considering replacement rather than repair the decision becomes a matter of utilization priorities. The Panasonic EZ series (2007 and newer) have well documented bugs and design flaws that were not present in the DMR-ES46V. There are some workarounds for use with EZ series machines mentioned in other CD Freaks threads and at the AVS Forum.
If dubbing videotapes to DVD is a priority then the $130 flat-rate repair is the best option as the EZ series combo recorders do not have the FUNCTIONS menu-initiated copying features that made the DMR-ES46V, DMR-ES35V, DMR-ES45V and DMR-ES30V such outstanding dubbing/copying workhorses. The EZ series combo recorders are limited to front panel control for internal dubbing/copying that yields unsatisfactory results, and headaches for the user, as detailed elsewhere. See this post: