Late season (but before dormancy) pruning will just stimulate additional growth that will not have sufficient time to harden off before cold weather sets in and can lead to winter damage. Wait until the shrub has lost all its leaves or better yet, wait until late winter just before it emerges from dormancy.

I'm not sure what you mean by moving 'pieces' of it. While it is often sold as a multi-stemmed shrub, it doesn't really sucker so doesn't have 'pieces' :-) In most cases, shrubs are not divided or split apart like a perennial.

Maybe the verb was intended as 'remove' rather than 'move'?

the usual default. is to prune after flowering.. which would have been mid spring ... so i would suggest you do it next spring ...

just take some stout twine.. or rope ... and tie it up a bit just to get it off the path ...

you would probably be better off doing rejuvenation pruning.. rather than a hair cut.. or random removal of one side of the shrub .... and once it is leafless .... you will get a better idea of the structure inside ...

i used to love this plant ... but mine eventually all died out.. due to some random disease .. of which i did not ID.. nor treat ....

i dont see many around town.. i wonder if its a MI thing ... and i would call them.. in my experience.. a short lived shrub .... lol.. guess that kinda went without saying... lol ..

ken

4th link states after flowering ...note the latin name : https://duckduckgo.com/?q=rejuvenation+pruning+Prunus+glandulosa+%27Rosea%27&t=ffcm&ia=web

my point.. if i had one .... [never say that to your spouse.. during an argument ... lol] ... is if someone can ID the disease ... it might be a variable in HOW you prune ... some level of sanitation ....

ken

http://extension.illinois.edu/hortanswers/plantdetail.cfm?PlantID=364&PlantTypeID=8

moo U source

http://msue.anr.msu.edu/news/plum_pox_virus_and_the_nursery_industry