As per my calculations regarding the F-F Beam with Central Load: Case-1D - CONCENTRIC INTERMEDIATE LOAD; LEFT END FIXED; RIGHT END FIXED.

Reference Roark's Formulas for Stress and Strain
Writer: Warren C. Young
6th Edition.

L = 120 in
Do = 4.50 in
t = 0.237 in
E = 29.5E6 lb/in^2
Di = 4.026 in
P = -1000 lb

*** Theoratical Caesar II 5.10 % Error X-software % Error
1-Deflection 0.0042 -0.0024 -42.86 -0.0046 9.52
2-Reaction A -500 -53.9 -89.22 -554 10.80
3-Reaction B -500 -53.9 -89.22 -554 10.80
4-Moment A -1250 -89.83 -92.81 -1340 7.20
5-Moment B 1250 89.83 -92.81 1340 7.20

Units:
Deflection in inches
Reaction in lbs
Moments in lbs-ft

Clearly Caesar II giving very much less reaction loads as any other software or calculation can predict.

I have also attached mathcad calculation file for Roark's Theoretical formulas I used.

Deflection is same i.e -WL3/192EI etc please see attached file.

Please let me know for any corrections or comments.