Post is a couple months old, but having worked for a commercial property management company may have some experience.
TLDR: Don't feel scammed or overcharged this will be typically of any PM company. As long as you aren't being stolen from and their doing a good job leasing/managing tenants I would work with them on the other minor stuff. PM isn't hired to work on property, but manage the processes.
Some of those charges you'd hope to be within their monthly fee are normal. That % is to cover known overhead expenses, admin fees, etc.
Anything unknown like inspections, lock changes, etc., my guess is they have a handyman subcontracted to perform who charges the PM company who then if you lucky passes cost to you, or likely marks up 10-25%. Seems expensive for $20-40 lock work, but it's not worth their time to go to the property for much less. They can't and won't include that in their monthly management fee because they have no idea what their contractor will charge them before signing a PM agreement and if they do it themselves it's little bit extra $$.
It's also, not an excuse, typical for information to not get relayed from a vendor/landscaper, to the PM, to you when it comes to misc things like bike laying in lawn. Can be for various reasons, but not end of the world and I would just remind them to please stay on top of things like this. If they weren't aware or address major issues like leaks, hazards, etc. that's when I'd be worried about their ability to manage.
In regards to being billed months late normally they won't charge you until their charged by contractor/landscaper, and just know their probably using joe blows landscaping who knows how to haul around a mower but probably not the most attentive to administrative/billing of their own business. Making it worse is if being billed monthly, that landscaper won't invoice the Pm company until end of month, most times a week or two into the following month, and if truly bad they struggle to get invoices from contractors at all, but again they can't bill you until they receive an invoice.
Any issues you are having with maintenance, inspections, fees (outside leasing related) likely not the PMs fault it's the vendors their using. Of course it's their job to manage this so you have a right to question charges and prompt work, but you need to work with them on a process so you can manage your financials better. Switching companies if everything else is good especially being able to find good tenants won't solve your concerns.
Recommendations:
1) Get agreement that you won't pay charges over 30 days late. i.e. late lawn charges. they should be able to put same agreement to their vendor to put pressure on them to bill on time, or make a vendor change. I have customers who won't pay past 60 days so puts pressure on me to assure my vendors bill me timely, and in my service agreements with them have same rules in place. If past that date I'm not getting paid, so my vendors aren't and if it happens multiple times I switch vendors and part of that monthly mgmt % is for my time to manage this process and/or find better services for you.
2) Get agreement on flat fees for the various routine cost such as landscaping, inspections, lock changes, etc, and require them to submit their vendor invoices as backup. This way you can confirm they aren't marking them up, and any non routine charges require them to get multiple bids. Bit extra work on your part at first to assure everything is square. If over time you feel better about their transparency you won't have to look through the back up as critically.
3) Require some sort of monthly report, if you don't already especially if managing remotely, that includes pictures. This helps to assure vendors are being conscious of unusual issues at property, the PM company who I'm sure doesn't see the property in person as much as you think has visuals to see if say a bike is laying in yard and landscaper just mowed around it or trashy, and if you see those issues in report without comments it was taken care of express your displeasure the PM company isn't doing job to your standards.
