Can anyone advise?

Code:
. use "Z:\Data\jt\survival.dta"
. capture erase "Z:\Data\jt\file.dta"

. gsort -delta _t n_eid

. gen myid=_n

. count if delta==1
127

. local numcases=r(N)

. set seed 6780591

. forvalues k=1(1)`numcases' {
2. preserve
3. gen case=1 if myid==`k'
4. sort case
5. gen time_case=_t[1]
6. gen gender_case=gender[1]
7. gen yob_case=yob[1]
8. keep if (case==1 | _t>time_case)
9. drop if gender!=gender_case
10. gen D=((yob-yob_case)^2)^0.5
11. gen U=runiform()
12. sort case D U
13. keep if _n<=6
14. gen set=`k'
15. recode case .=0
16. keep set case n_eid _t
17. capture save "Z:\Data\jt\file.dta"
18. if _rc!=0 {
19. append using "Z:\Data\jt\file.dta"
20. save "Z:\Data\jt\file.dta", replace
21. }
22. restore
23. }
already preserved
r(621);

. use "Z:\Data\jt\file.dta", clear
file Z:\Data\jt\file.dta not found
r(601);

.