Bug also appears with LO 6.4.7.2. Could be a very old bug. See https://bugs.documentfoundation.org/show_bug.cgi?id=91879

Confirming with

Version: 7.4.1.2 / LibreOffice Community aarch64 macOS Silicon 
Build ID: 3c58a8f3a960df8bc8fd77b461821e42c061c5f0
CPU threads: 8; OS: Mac OS X 13.0; UI render: default; VCL: osx
Locale: fr-FR (fr_FR.UTF-8); UI: fr-FR
Calc: threaded

I can confirm the bug.

I've observed that, in the form "Form", when the button is clicked and the message appears, the button doesn't loss the focus (the background continue colored) and when the mouse over, the focus disappears (and then the record moves), while in the "Form_whitout_messagebos" just clicking the button lost the focus.


Tested with:
--------------------------
Version: 7.4.2.3 (x64) / LibreOffice Community
Build ID: 382eef1f22670f7f4118c8c2dd222ec7ad009daf
CPU threads: 4; OS: Windows 10.0 Build 19045; UI render: Skia/Raster; VCL: win
Locale: es-ES (es_ES); UI: es-ES
Calc: CL
--------------------------
Versión: 6.4.7.2 (x64)
Id. de compilación: 639b8ac485750d5696d7590a72ef1b496725cfb5
Subprocs. CPU: 4; SO: Windows 10.0 Build 19045; Repres. IU: predet.; VCL: win; 
Configuración regional: es-ES (es_ES); Idioma de IU: es-ES
Calc: CL

(In reply to jcsanz from comment #3)
> I can confirm the bug.
> 
> I've observed that, in the form "Form", when the button is clicked and the
> message appears, the button doesn't loss the focus (the background continue
> colored)

Can't see this by a colored background, but if I click, after clicked on "OK", on the background of the form, there won't be happen anything when moving mouse over the navigation bar.

Bug will be a little bit different in older versions of LO:
LO 7.1.5.2: 
Click on navigation bar 'Next Record'. 
Message box appears again. 
Next record will be shown.
Message box appears again. 
Next record will be shown.
→ Message box appears tow times and directly, also moved 2 rows 

This changed with first version of LO 7.3.0.3 to the described behavior with moving mouse over navigation bar and changing to 'Next Record'.

@jcsanz: Please don't change Version of the bug to newer version. It has to be the oldest version. So it will be easier to find the reason for the buggy behavior.

(In reply to Robert Großkopf from comment #4)

> 
> @jcsanz: Please don't change Version of the bug to newer version. It has to
> be the oldest version. So it will be easier to find the reason for the buggy
> behavior.

I hadn't changed, but then, the version should be 6.4.7.2, shouldn't it?
If so, can you change it, please

(In reply to jcsanz from comment #5)
> (In reply to Robert Großkopf from comment #4)
> 
> I hadn't changed, but then, the version should be 6.4.7.2, shouldn't it?
> If so, can you change it, please

Have a look at "Modified" → History. There is reported your account for changing.

See comment 4: The behavior changed here from LO 7.2.5.2 to LO 7.3.0.3. In earlier versions the message box appears two times here. 
Might be it is different in Window, but it is the buggy behavior, which I could confirm for OpenSUSE 15.3 64bit rpm Linux and VCL:kf5 since LO 7.3.0.3

(In reply to Robert Großkopf from comment #6)

> Have a look at "Modified" → History. There is reported your account for
> changing.
So, sorry by that, but I've never realized I'd changed ¡three! different fields

Have had a problem similar to this. Could solve it by adding 
Wait 500
in macro.
With

Sub Check_rl_term_context(oEvent AS OBJECT)
	oForm = oEvent.Source
	IF hasUnoInterfaces(oForm, "com.sun.star.form.XForm" ) THEN
		Wait 500
		MsgBox("Test")
	END IF
End Sub

I could move the mouse where ever I want. No next or previous row will appear. 

But the bug is still there: A button, which hasn't been pressed, should never execute anything.

It is behaving like a mouse-over event trigger. Definitely a bug,  but where? XListener interface ?

Bug is still the same with
Version: 24.8.3.1 (X86_64) / LibreOffice Community
Build ID: 65412f067af443213e726c93f137ccc85c9a1e06
CPU threads: 6; OS: Linux 6.4; UI render: default; VCL: kf5 (cairo+xcb)
Locale: de-DE (de_DE.UTF-8); UI: de-DE
Calc: threaded