First a side-note: I have changed the text format of your post from "Plain text" to "Filtered HTML", because its "plain text" contained HTML codes. It looks much nicer this way

but when I press encoder 5 it is the same as if I pressed encoder 4:
encoder 5: $80 36 0

and if I press encoder 7 it is as if I press many encoders at once.

I can think of two causes for this behavior:

1. A software problem:
This behavior could simply be what has been defined for these encoders in the current preset on the BCF2000.
To study the definition of the current ("temporary") preset, you can load it into BC Manager:
From the "B-Controls" window, open the "Presets" window, make sure the first line ("No. 0") is selected (highlighted), then perform MIDI -> Receive. After the preset definition has been loaded, you can study the push encoder definitions in the Layout window and the Buttons window.

2. A hardware problem:
There might be a hardware error in your BCF2000, causing one push encoder to trigger other ones.
This doesn't seem likely, but people have indeed reported problems like this.

Hope this helps,
   Mark.

I also have a similar problem with button 91 that when I press it it acts on buttons 89, 90, 92, 95 (Store), 96 (Learn), 97 (Edit) and 98 (Exit) but in an arbitrary way (every time I press it it turns some of these on or off).
Is this a hardware problem?

Side-note: the BCF's buttons (including its push encoders) are numbered from 1 to 64, so I suppose you're talking about the Control Change messages associated with certain buttons in a certain preset here.

Anyway, before concluding that the problems with these buttons and with push encoder 7 are hardware-related, you might try the following things (if you haven't already):

• Upload a "simple" preset to the BCF's "temporary preset" in which each BCF element outputs a particular Control Change message. (You can set up such a preset from scratch easily in BC Manager, but a good one is Behringer's standard "all controls" preset, which can be found in Factory_Presets_BCF.zip, available from the "Factory presets" folder in the B-Control user files section of this website.) After uploading this preset to the BCF, press/turn the BCF's elements one after another and see what happens on the BCF itself and what MIDI output the BCF produces. For instance: does push encoder 7 still trigger the other ones? (An interesting question suddenly occurring to me: does this behavior occur in all four Encoder Groups?) To determine whether each BCF element outputs the correct MIDI message when you press/turn it, you can open BC Manager's "MIDI input messages" window and press "Record".
• Try BC Manager's "Test hardware" mode (accessible via MIDI -> Maintenance in the "B-Controls" window); see section 10 of the BC Manager manual for discussion of this mode. This mode doesn't address your specific problems, but you might discover certain other hardware problems.

If your problems are hardware-related, I'm not the most qualified person to help you.
I did write a guide describing how to open a BCF/BCR2000 without breaking the small tabs on the side-panels.
Once you've opened your BCF, you could start by trying to clean the misbehaving button(s)/encoder(s), perhaps applying some blower or special spray.
I vaguely remember reading discussions in which people mentioned particular types of buttons or encoders that could be bought as replacements, but this might have been on the (recently terminated) Yahoo BC2000 forum. And note that the fault might lie somewhere else than in a button or encoder: it could be in a printed circuit, or even in a chip. There comes a point where the trouble you'd have buying replacements of (suspected) defective parts and actually replacing these parts isn't worth the effort.

   Mark.