Add root files

Dear experts,
when I try to add about 10000 root file, at some point I have the error message [1]. Is it related to the high number of root file? Is there a limit on the number of root file when we want to add? If not, is there an option to avoid this problem?
Regards

[1]

hadd Opening the next 883 files
hadd Target path: DYJetsM50.root:/
hadd Target path: DYJetsM50.root:/h2taus
hadd Target path: DYJetsM50.root:/h2taus/sync
Error R__unzip_header: error in header
Info in TFileMerger::MergeRecursive: could not read object for key {nevt, Initial number of event}
Error R__unzip_header: error in header
Info in TFileMerger::MergeRecursive: could not read object for key {mt, mt}
Error R__unzip_header: error in header
Info in TFileMerger::MergeRecursive: could not read object for key {et, et}
Error R__unzip_header: error in header
Info in TFileMerger::MergeRecursive: could not read object for key {tt, tt}
Error R__unzip_header: error in header
Info in TFileMerger::MergeRecursive: could not read object for key {em, em}
hadd Target path: DYJetsM50.root:/h2taus/h2taus
Error R__unzip_header: error in header

Dear experts,

do you have any idea what this error message means?

Regards

Can it be that, while writing the new file, some object reaches the magic cycle number 9999?

Dear Pepe,
sorry, what is the “magic cycle number 9999”? So you mean it has nothing to due to the big number?
Regards

BTW. Have you tried to “hadd -n 100 …”?

I tried “hadd -n 100” but I still have the error[1].
Regards

[1]
hadd Opening the next 99 files
hadd Target path: DYJetsM50.root:/
hadd Target path: DYJetsM50.root:/h2taus
hadd Target path: DYJetsM50.root:/h2taus/sync
Error R__unzip_header: error in header
Info in TFileMerger::MergeRecursive: could not read object for key {nevt, Initial number of event}
Error R__unzip_header: error in header
Info in TFileMerger::MergeRecursive: could not read object for key {mt, mt}
Error R__unzip_header: error in header
Info in TFileMerger::MergeRecursive: could not read object for key {et, et}
Error R__unzip_header: error in header
Info in TFileMerger::MergeRecursive: could not read object for key {tt, tt}
Error R__unzip_header: error in header
Info in TFileMerger::MergeRecursive: could not read object for key {em, em}
hadd Target path: DYJetsM50.root:/h2taus/h2taus
Error R__unzip_header: error in header