Libre office unresponsive and high CPU with large document

[mymsman]

I have a large document 1070kB with NO graphics that when loaded in LO Writer is slow to load and after loading LO consumes 30% CPU and is unresponsive,

The document was created by Mail merge and consists of almost 2000 tables and nearly 4000 pages - the creation by mail merge wizard was slow but problem free

Many other problems with large documents seem to be related included images but my document has no images at all.

Can anybody suggest any solution - I don’t really want to generate 2000 files from mail merge.

[paul1149]

What hardware? What OS? Which LO? Bitness of both?

One thing that helped me with large copy/paste operations doing this was to Import the data into a new document rather than copy/paste.

[mymsman]

Windows 10 64 bit, HP 4 core laptop, LO 32 bit

Libre Office
Version: 5.1.6.2
Build ID: 07ac168c60a517dba0f0d7bc7540f5afa45f0909
CPU Threads: 4; OS Version: Windows 6.2; UI Render: default;
Locale: en-GB (en_GB); Calc: CL

I have discovered that if I save the file as .html rather than .odt my problems disappear
No high cpu or sluggishness

Odd that file type should make such a significant difference

UPDATE

Alas with the latest version of LO my workaround of using .html no longer works

Version: 5.4.2.2 (x64)
Build ID: 22b09f6418e8c2d508a9eaf86b2399209b0990f4
CPU threads: 4; OS: Windows 6.19; UI render: default;
Locale: en-GB (en_GB); Calc: group

Whatever format of source file I use LO consumes 30% cpu

I fear I will have to downgrade to an older version of LO